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experimental tests on a Pre-Heated Combustion Chamber for Ultra Micro Gas Turbine Device: Air/Fuel Ratio Evaluation

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Engineering（科研） 2016年第11期8卷 789-805页

作者： Roberto Capata Kliton Kylykbashi Alfonso Calabria Mario Di Veroli Department of Mechanical and Aerospace Engineering University of Roma “Sapienza” Roma Italy

Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.

关键词： experimental tests Combustion Chamber Ultra Micro Gas Turbine Fuel Consumption

experimental investigation on ice-breaking performance of a novel plasma striker

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Chinese Journal of Aeronautics 2022年第1期35卷 307-317页

作者： Tianxiang GAO Zhenbing LUO Yan ZHOU Shengke YANG Wenqiang PENG Xiong DENG Pan CHENG College of Aerospace Engineering National University of Defense TechnologyChangsha 410073China China Aerodynamics Research and Development Center Mianyang 621000China

Aircraft icing has long been a plague to aviation for its serious threat to flight safety.Recently,researches about a newly proposed deicing method based on Plasma Synthetic Jet Actuator(PSJA)have just started.To meet the requirements of in-flight deicing,structure of PSJA needs to be adjusted.This paper completed the detailed design and experimental validation of a novel plasma striker,which was a modified version of PSJA.Influences of mass of the moving part and rod shapes on the ice-breaking performances were also studied.Besides,a“conical-nosed rod configuration”was proposed.Its purpose was to ensure a good ice-breaking performance of the plasma striker on long ice,by generating a splitting failure.Results show that,though mass of the moving part was just several grams,ice-breaking performance was better when the mass was lighter.The rectangular rod could generate an elliptical circumferential crack,whose major axis was parallel to the direction of the long side of the rectangular rod.And the“conical-nosed rod”concept was verified to be able to generate a splitting crack which can spread completely to the far end of long ice,and the crack direction was parallel to edge line of the cone.In general,the plasma striker has the advantages of simple structure,low energy consumption,little harm to the flow field and the aircraft skin.Simulations will be carried out in future works to study in detail the working process of the plasma striker.

关键词： Conical shaped rod Deicing experimental tests High-speed photography Ice fracture Plasma striker

Impact of aperture on dynamic response of sandwich plates with aluminium face-sheets and PMI core based on an alternative finite element formulation and experiments

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Chinese Journal of Aeronautics 2022年第4期35卷 266-280页

作者： Zhen WU Yongzhi LI Dongjian ZHANG Jie MEI Xiaohui REN Rui MA School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China School of Mechanical Engineering Xi an Aeronautical UniversityXi'an 710065China

Apertures generally exist in the sandwich structures attributing to mechanical connection and lightweight, which might induce failure of such structures. Thus, it is required to realize the impact of aperture on mechanical behaviors of sandwich structures. If transverse shear deformations are unable to be described accurately, the reasonable prediction of dynamic behaviors of the form-core sandwich plates with apertures will meet severe challenges due to a large difference of transverse shear modulus at the adjacent layers. Thereby, such issue is less studied by using the efficient models and experimental testing, so an alternative sinusoidal-type finite element formulation is to be proposed to precisely predict dynamic response of the form-core sandwich structures with apertures. The proposed finite element formulation can meet beforehand compatible conditions of transverse shear stresses at the interfaces of adjacent laminates. In order to appraise strictly capability of the proposed model, experimental tests on natural frequencies of three groups of specimens with different apertures have been carried out. Moreover, four specimens in each group are tested to reduce the testing errors, which is less reported in the published literature. In addition,three-dimensional Finite Element Method(3-D FEM) is also selected to account for the good performance of the present model. Finally, the impact of aperture diameter on the natural frequencies of the sandwich structures is both experimentally and numerically investigated, which can serve as a reference for other researchers.

关键词： Dynamic response Sandwich plates Higher-order theory experimental tests Finite element method

Influence and experiment of cable-net manufacturing errors on surface accuracy of mesh reflector antennas

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Chinese Journal of Aeronautics 2023年第2期36卷 363-376页

作者： Zihan SUN Baoyan DUAN Yiqun Zhang Dongwu YANG School of Electromechanical Engineering Xidian UniversityXi'an 710071China

Cable-net structures are of substantial importance in the construction of large mesh reflector antennas.Owing to the inevitable errors in their manufacturing process,the reflector surface accuracy deteriorates.This study makes a comprehensive investigation of random manufacturing errors during constructing the mesh reflector antennas,and analyze its influence on reflector surface accuracy.Firstly,the sensitivity of reflector surface accuracy with respect to the random errors of the unstressed cable length is mathematically deducted.Secondly,a non-button connecting method is proposed and analyzed to reduce manufacturing errors.Thirdly,two physical experiment models based on 2.62-meter mesh reflector antenna are made.Finally,numerical examples and experimental tests are given to demonstrate the effectiveness of the proposed method.Compared with the traditional method,the proposed method can effectively reduce the influence of the manufacturing errors on the reflector surface accuracy.Moreover,the reduction in the sizes of the nodes also reduces the risk of entanglement of the mesh reflector antenna during the deployment process,and thereby improves the deployment reliability.

关键词： Error analysis experimental tests Manufacturing methods Reflector antenna Surface accuracy

Reflection and Transmission of Regular Waves from/Through Single and Double Perforated Thin Walls

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China Ocean Engineering 2017年第4期31卷 466-475页

作者： Nadji CHIOUKH Esin CEVIK Yalcin YUKSEL Department of Civil Engineering University of Djillali Liabes Sidi Bel-Abbes 22000 Algeria Laboratory of Naval Aero-Hydrodynamics Department of Maritime Engineering USTO MB Oran 31000 Algeria Department of Civil Engineering Yildiz Technical University Istanbul Turkey

In this paper, reflection and transmission coefficients of regular waves from/through perforated thin walls are investigated. Small scale laboratory tests have been performed in a wave flume firstly with single perforated thin Plexiglas plates of various porosities. The plate is placed perpendicular to the flume with the height from the flume bottom to the position above water surface. With this thin wall in the flume wave overtopping is prohibited and incident waves are able to transmit. The porosities of the walls are achieved by perforating the plates with circular holes. Model settings with double perforated walls parallel to each other forming so called chamber system, have been also examined. Several parameters have been used for correlating the laboratory tests’ results. experimental data are also compared with results from the numerical model by applying the multi-domain boundary element method （MDBEM） with linear wave theory. Wave energy dissipation due to the perforations of the thin wall has been represented by a simple yet effective porosity parameter in the model. The numerical model with the MDBEM has been further validated against the previously published data.

关键词： wave-structure interaction perforated thin walls boundary element experimental tests wave reflection wave transmission

An experimental investigation on the effect of grain size on oil-well sand production

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Petroleum Science 2012年第3期9卷 343-353页

作者： Vahidoddin Fattahpour Mahdi Moosavi Mahdi Mehranpour School of Mining Engineering the University of Tehran

Sand production in oil wells is closely related to the mechanical behavior and petrographical properties of sandstones reservoir. Grain size is one of the main parameters controlling the phenomenon, which is studied in this paper. Large-scale hollow cylindrical synthetic samples with the same rock strength but different grain sizes were tested by an experimental setup in the laboratory. Different external stresses and fluid flow rates were applied to the samples and produced sand was measured continuously. Results show two different trends between sanding stress level and grain size. For the samples with finer grain size （D50〈0.3 mm）, the required confining stress for different sanding levels decreased with an increase in the grain size and for the samples with the coarser grains （D50〉0.3 mm） the required confining stress for different sanding levels dramatically increased with an increase in the grain size. Those two different trends were discussed and explained. The first one was production of individual grains and the second was bigger chunks in the slab form. In samples with large grains, plastic zones around hole were changed to a completely loose zone including interlocked individual grains or cluster of grains. In these samples after breakage of these interlocked zones sand was produced in the form of individual grains and clusters. Contrary to this, for samples with smaller grain size, shear bands were formed around the plastified hole and sand was produced in the form of big chunks or slabs.

关键词： Sand production experimental tests grain size perforation size

Elucidating the operating behavior of PEM fuel cell with nickel foam as cathode flow field

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Science China(Technological Sciences) 2021年第5期64卷 1041-1056页

作者： HUO Sen SHI WeiYu WANG RenFang LU BingBing WANG Yang JIAO Kui HOU ZhongJun Shanghai Hydrogen Propulsion Technology Co. Ltd.Shanghai 201804China State Key Laboratory of Engines Tianjin UniversityTianjin 300350China

Metal foam material,which serves as an alternative replacement of the conventional flow distributor of proton exchange membrane(PEM)fuel cell,has been attracting much attention over last few decades.In this work,three-dimensional modeling work for PEM fuel cell containing metal foam as cathode flow distributor has been carried out.The fuel cell performance and operating characteristics of metal foam flow field and conventional parallel flow channel have been compared and discussed.The cell performance has been reasonably validated based on the corresponding experimental tests conducted in this study.The superior performance of PEM fuel cell with metal foam as cathode flow field benefits a lot from the uniform gas flow.The porous metal foam material provides more pathways for the water delivery at the interface of metal foam flow field and gas diffusion layer(GDL),accelerating water removal capability of cathode.Because of the significant oxygen transfer loss in diffusion limited parallel channel,the operation of PEM fuel cell with parallel channel is found to be more sensitive to cathode humidification and oxygen supply at inlet.Due to the more uniform and effective electron transport though the porous electrode,it is possible to use thinner GDL in metal foam PEM fuel cell.It is expected that this study could give a good baseline of operating behavior of PEM fuel cell with metal foam flow distributor.

关键词： proton exchange membrane fuel cell metal foam flow field conventional parallel flow field numerical analysis experimental tests

FE modeling of concrete beams and columns reinforced with FRP composites

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Defence Technology（防务技术） 2021年第1期17卷 1-14页

作者： Farid Abed Chahmi Oucif Yousef Awera Haya H.Mhanna Hakem Alkhraisha Department of Civil Engineering American University of SharjahP.O.Box 26666United Arab Emirates Institute of Structural Mechanics(ISM) Bauhaus-Universitat WeimarMarienstraße 15D-99423WeimarGermany

Compression and flexure members such as columns and beams are critical in a structure as its failure could lead to the collapse of the structure.In the present work,numerical analysis of square and circle short columns,and reinforced concrete(RC)beams reinforced with fiber reinforced polymer composites are carried out.This work is divided into two parts.In the first part,numerical study of axial behavior of square and circular concrete columns reinforced with Glass Fiber Reinforced Polymer(GFRP)and Basalt Fiber Reinforced Polymer(BFRP)bars and spiral,and Carbon Fiber Reinforced Polymer(CFRP)wraps is conducted.The results of the first part showed that the axial capacity of the circular RC columns reinforced with GFRP increases with the increase of the longitudinal reinforcement ratio.In addition,the results of the numerical analysis showed good correlation with the experimental ones.An interaction diagram for BFRP RC columns is also developed with considering various eccentricities.The results of numerical modeling of RC columns strengthened with CFRP wraps revealed that the number and the spacing between the CFRP wraps provide different levels of ductility enhancement to the column.For the cases considered in this study,column with two middle closely spaced CFRP wraps demonstrated the best performance.In the second part of this research,flexural behavior of RC beams reinforced with BFRP,GFRP and CFRP bars is investigated along with validation of the numerical model with the experimental tests.The results resembled the experimental observations that indicate significant effect of the FRP bar diameter and type ont he flexural capacity of the RC beams.It was also shown that Increasing the number of bars while keeping the same reinforcement ratio enhanced the stiffness of the RC beam.

关键词： Numerical analysis BRFP GFRP CFRP Columns Beams experimental tests

Optimization of Baffled Rectangular and Prismatic Storage Tank Against the Sloshing Phenomenon

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China Ocean Engineering 2020年第5期34卷 664-676页

作者： Hassan SAGHI NING De-zhi CONG Pei-wen ZHAO Ming Department of Civil Engineering Hakim Sabzevari UniversitySabzevar ***Iran State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China School of Computing Engineering and MathematicsUniversity of Western SydneyPenrithNSW 2751Australia

The fluid motion in partially filled tanks with internal baffles has wide engineering applications. The installation of baffles is expected to reduce the effect of sloshing as well as the consequent environmental damages. In the present study, a series of experimental tests are performed to investigate the sloshing phenomenon in a baffled rectangular storage tank. In addition, the sloshing phenomenon is also modeled by using Open Foam. Based on the experimental and numerical studies, optimization of the geometric parameters of the tank is performed based on some criteria such as tank area, entropy generation, and the horizontal force exerted on the tank area due to the sloshing phenomenon.The optimization is also carried out based on the entropy generation minimization analysis. It is noted that the optimum baffle height is in the range of h_b/h_w=0.5-0.75 in the present study(where h_b and h_w are the baffle height and water depth, respectively). Based on the results, the optimal design of the tank is achieved with R_A= 0.9-1.0(where R_A=L/W, L and W are the length and width of the tank, respectively). The results also show that the increase of h_b can lead to a decrease of the maximum pressure and horizontal force exerted on the tank. It is also noted that the horizontal force exerted on the tank firstly continues to increase as the sway motion amplitude increases.However, as the normalized motion amplitude parameter, a/L(The parameter a is the motion amplitude), exceeds0.067, the effect of motion amplitude on the force is not obvious. The same optimization is also performed in the multiple-variable-baffled tank and prismatic storage tank.

关键词： baffled rectangular storage tank experimental tests sloshing phenomenon optimization entropy generation Open Foam