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Experimental investigation on coal pore-fracture variation and fractal characteristics synergistically affected by solvents for improving clean gas extraction

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International Journal of Mining Science and Technology 2024年第3期34卷 413-425页

作者： Feilin Han Sheng Xue Chunshan Zheng Zhongwei Chen Guofu Li Bingyou Jiang Key Laboratory of Safe and Effective Coal Mining of Ministry of Education Anhui University of Science and TechnologyHuainan 232001China School of Safety Science and Engineering Anhui University of Science and TechnologyHuainan 232001China School of Mechanical and Mining Engineering University of QueenslandQLD 4072Australia State Key Laboratory of Coal and Coalbed Methane Co-Mining Jincheng 048012China

Chemical solvents instead of pure water being as hydraulic fracturing fluid could effectively increase permeability and improve clean methane extraction efficiency.However,pore-fracture variation features of lean coal synergistically affected by solvents have not been fully understood.Ultrasonic testing,nuclear magnetic resonance analysis,liquid phase mass spectrometry was adopted to comprehensively analyze pore-fracture change characteristics of lean coal treated by combined solvent(NMP and CS_(2)).Meanwhile,quantitative characterization of above changing properties was conducted using geometric fractal theory.Relationship model between permeability,fractal dimension and porosity were established.Results indicate that the end face fractures of coal are well developed after CS2and combined solvent treatments,of which,end face box-counting fractal dimensions range from 1.1227 to 1.4767.Maximum decreases in ultrasonic longitudinal wave velocity of coal affected by NMP,CS_(2)and combined solvent are 2.700%,20.521%,22.454%,respectively.Solvent treatments could lead to increasing amount of both mesopores and macropores.Decrease ratio of fractal dimension Dsis 0.259%–2.159%,while permeability increases ratio of NMR ranges from 0.1904 to 6.4486.Meanwhile,combined solvent could dissolve coal polar and non-polar small molecules and expand flow space.Results could provide reference for solvent selection and parameter optimization of permeability-enhancement technology.

关键词： Clean gas extraction Chemical solvent Experimental investigation Fractal characteristics Pore fracture

Establishment of a sediment transport capacity equation on loessal slope via Experimental investigation

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International Journal of Sediment Research 2023年第2期38卷 166-174页

作者： Tian Wang Jingsi Li Jingming Hou Peng Li Shengdong Cheng Feng Wang Wen Wang Zhanbin Li Reinhard Hinkelmann State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China Xi'an University of Technology Chair of Water Resources Management and Modeling of Hydrosystems Department of Civil Engineering Technische Universit at Berlin Shaanxi Province Institute of Water Resources and Electric Power investigation and Design Key Laboratory of National Forestry Administration on Ecological Hydrology and Disaster Prevention in Arid Regions Xi'an University of Technology

Areliable sediment transport capacity function provides response against challenges of soil erosion prediction on the Loess Plateau of China. The popular sediment transport capacity functions are questionable on loess slopes because the experimental conditions from which they were derived, like bed materials, gentle slopes,and surface roughness, are different from soil erosion processes on the loess slopes. Due to the foregoing uncertainty, a suitable sediment transport capacity function was developed based on a flume experiment investigation. The erodible bed experiment was implemented for five unit width discharges(1.3 × 10-4-3.3 × 10-4m2/s) and ten slopes(5.2%-57.7%). The selected sediment transport capacity equations were tested in an applicability evaluation. The results of this evaluation found that the Govers(1990) function had the best performance(P.O.0.5-2.0= 76%, R2= 0.93, RMSE = 0.03 kg/(m·s)), followed by the Yalin(1963) function(P.O.0.5-2.0= 80%, R2= 0.81, RMSE = 0.05 kg/(m·s)), and finally by the Low(1989) function(P.O.0.5-2.0= 72%,R2= 0.79, RMSE = 0.04 kg/(m·s)), where P.O.0.5-2.0is the percentage of estimated values with logarithmic discrepancies with the measured value between 0.5 and 2.0; R2is the coefficient of determination and RMSE is the roof mean squares error. The cohesive sediment incipient motion velocity is introduced into the Govers(1990) function, and the sediment particle parameter is determined from measured experimental data. The developed sediment transport capacity equation has good performance with predicted values corresponding to measured values(P.O.0.5-2.0= 98%, R2= 0.98, RMSE = 0.006 kg/(m·s)). The research results provide an improved sediment transport capacity function on the basis of experiments for steep loessal slopes.

关键词： Experimental investigation Hydraulic conditions Loessal slope Sediment transport capacity

Experimental investigation on the Strength and Ductility Performance of Steel-Timber-Steel Joints with Screw and Steel-Tube Fasteners

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Journal of Renewable Materials 2023年第12期11卷 4175-4195页

作者： Huifeng Yang Mingwang Wu Rixin Gu Hang Cao Kai Xiao Benkai Shi College of Civil Engineering Nanjing Tech UniversityNanjing211816China

This article presents experimental results of steel-timber-steel(STS)joints loaded parallel to grain.Eight groups of specimens were designed,and tensile tests were performed.The fastener types and fastener numbers were considered to evaluate the tensile strengths and ductility performances of the STS joints.The screws with 6 mm diameter and the innovative steel-tubes with 18 mm diameter were adopted as connecting fasteners.The experimental results were discussed in terms of yielding and ultimate strengths,slip stiffness,and ductility factors.The ductility classification and failure mechanisms of each group of specimens were analyzed.It was demonstrated that the STS joint with large diameter steel-tubes showed acceptable ductility,which was close to the ductility of the STS joint with small diameter screws,thanks to the hollow structure of the steel-tube.The theoretical strengths of various failure modes for the joints with small diameter screws or large diameter steel-tubes were calculated and compared with the experimental results.The ductile performance of the STS joint was discussed by comparing the theoretical strengths of various failure modes.The effective number of the STS joint with multifasteners was also analyzed by considering the failure mechanisms in aspects of tensile strength and slip stiffness.

关键词： Steel-timber-steel joint screw steel-tube ductility Experimental investigation timber structure

Unsteady experimental and numerical investigation of aerodynamic performance in ultra-high-lift LPT

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Chinese Journal of Aeronautics 2020年第5期33卷 1421-1432页

作者： Xiao QU Yanfeng ZHANG Xingen LU Junqiang ZHU Key Laboratory of Light-Duty Gas-Turbine Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100190China

Detailed experimental and numerical investigations were performed for an ultra-high-lift front-loaded low-pressure turbine cascade (Zw=1.58) with periodic wakes.The interaction mechanisms between the incoming wakes and endwall secondary flow were carefully examined.Wakes were produced by moving upstream rods,and flow field downstream of the cascade was measured using a seven-hole probe.experimental results revealed that incoming wakes influenced not only the boundary layer development of the blade suction surface but also the complex endwall secondary vortex structures.On the suction surface:Incoming wakes clearly suppressed the suction side separation bubble at a low Reynolds number of 25000.Nevertheless,the effects of different wake passing frequencies were not significantly different at Re=100000,and the profile losses under wake passing were even greater than in the absence of wakes.At the end walls:Incoming wakes more strongly suppressed secondary flow at Re=100000 than at Re=25000,because the lowmomentum fluid inside the incoming wakes clearly increased the endwall cross-passage pressure gradient at Re=25000.The experimental results indicated that periodic wakes decreased the passage vortex and counter vortex core strength by 25% and 30%,respectively,at Re=100000.Instantaneous results also demonstrated that endwall secondary vortices decreased significantly near the position of wakes passing.

关键词： Experimental investigation Low pressure turbine Periodic wake Secondary flow Ultra-High-lift

Auto-parametric resonance of a continuous-beam-bridge model under two-point periodic excitation:an Experimental investigation and stability analysis

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Earthquake Engineering and Engineering Vibration 2024年第2期23卷 445-454页

作者： Li Yuchun Shen Chao Liu Wei Li Dong Department of Hydraulic Engineering College of Civil EngineeringTongji UniversityShanghai 200092China

The auto-parametric resonance of a continuous-beam bridge model subjected to a two-point periodic excitation is experimentally and numerically investigated in this study.An auto-parametric resonance experiment of the test model is conducted to observe and measure the auto-parametric resonance of a continuous beam under a two-point excitation on columns.The parametric vibration equation is established for the test model using the finite-element method.The auto-parametric resonance stability of the structure is analyzed by using Newmark's method and the energy-growth exponent method.The effects of the phase difference of the two-point excitation on the stability boundaries of auto-parametric resonance are studied for the test model.Compared with the experiment,the numerical instability predictions of auto-parametric resonance are consistent with the test phenomena,and the numerical stability boundaries of auto-parametric resonance agree with the experimental ones.For a continuous beam bridge,when the ratio of multipoint excitation frequency(applied to the columns)to natural frequency of the continuous girder is approximately equal to 2,the continuous beam may undergo a strong auto-parametric resonance.Combined with the present experiment and analysis,a hypothesis of Volgograd Bridge's serpentine vibration is discussed.

关键词： auto-parametric resonance continuous beam bridge model two-point excitation Experimental investigation stability analysis vibration of Volgograd Bridge

Sand transport in multiphase flow mixtures in a horizontal pipeline:An Experimental investigation

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Petroleum 2019年第2期5卷 161-170页

作者： Mariella Leporini Barbara Marchetti Francesco Corvaro Giuseppe di Giovine Fabio Polonara Alessandro Terenzi Universita Politecnica delle Marche AnconaItaly Universita Telematica eCampus Italy Construction Technologies Institute National Research Council(CNR)San Giuliano MilaneseMilanItaly Saipem SpA Italy

An inherent problem with both oil and natural gas production is the deposition of sand particles in pipeline,which could lead to problems such as excessive pressure drops,equipment failure,pipeline erosion,and production decline.The characterization of sand particles transport and sedimentation in different flow systems such as sandemultiphase mixtures is vital to predict the sand transport velocity and entrainment processes in oil and gas transportation pipelines.However,it seems that no model exists able to accurately characterize the sand transport and deposition in multiphase pipeline.In fact,in the last decade several researchers tried to extend the modeling of liquid-solid flow to gas-liquid-solid flow,but no significant results have been obtained,especially in slug flow condition due to the complexity of the phenomenon.In order to develop and validate a mathematical model properly formulated for the calculation of the sand critical deposition velocity in gas-liquid flow,more and more experimental data are necessary.This paper presents a preliminary experimental study of three phase flows(air-water-sand)inside a horizontal pipe and the application of the sand-liquid models present in literature.Significant observations were made during the experimental study from which several conclusions were drawn.Different sand flow regimes were established by physical observation and data analysis:fully dispersed solid flow,moving dunes and stationary bed.The critical deposition velocities were determined at different sand concentrations.It was concluded that sand transport characteristics and the critical deposition velocity are strongly dependent on the gas-liquid flow regime and on sand concentration.

关键词： Sand transport Multiphase flow Minimum transport condition Deposition Experimental investigation Oil and gas

Multi-objective Optimization Design and Experimental investigation of Centrifugal Fan Performance

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Chinese Journal of Mechanical Engineering 2013年第6期26卷 1267-1276页

作者： ZHANG Lei WANG Songling HU Chenxing ZHANG Qian Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education North China Electric Power University

Current studies of fan performance optimization mainly focus on two aspects： one is to improve the blade profile, and another is only to consider the influence of single impeller structural parameter on fan performance. However, there are few studies on the comprehensive effect of the key parameters such as blade number, exit stagger angle of blade and the impeller outlet width on the fan performance. The G4-73 backward centrifugal fan widely used in power plants is selected as the research object. Based on orthogonal design and BP neural network, a model for predicting the centrifugal fan performance parameters is established, and the maximum relative errors of the total pressure and efficiency are 0.974% and 0.333%, respectively. Multi-objective optimization of total pressure and efficiency of the fan is conducted with genetic algorithm, and the optimum combination of impeller structural parameters is proposed. The optimized parameters of blade number, exit stagger angle of blade and the impeller outlet width are seperately 14, 43.9~, and 21 cm. The experiments on centrifugal fan performance and noise are conducted before and after the installation of the new impeller The experimental results show that with the new impeller, the total pressure of fan increases significantly in total range of the flow rate, and the fan efficiency is improved when the relative flow is above 75%, also the high efficiency area is broadened. Additionally, in 65% -100% relative flow, the fan noise is reduced. Under the design operating condition, total pressure and efficiency of the fan are improved by 6.91% and 0.5%, respectively. This research sheds light on the considering of comprehensive effect of impeller structrual parameters on fan performance, and a new impeller can be designed to satisfy the engineering demand such as energy-saving, noise reduction or solving air pressure insufficiency for power plants.

关键词： centrifugal fan impeller structural parameters optimization Experimental investigation

Experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering boundary effect

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第3期16卷 1072-1084页

作者： Xuwei Wang Yeshuang Xu State Key Laboratory of Ocean Engineering School of Naval ArchitectureOceanand Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China Shanghai Key Laboratory for Digital Maintenance of Buildings and Infrastructure Department of Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

The boundary condition is a crucial factor affecting the permeability variation due to suffusion.An Experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering the boundary effect is conducted,where the hydraulic head difference(DH)varies,and the boundary includes non-loss and soil-loss conditions.Soil samples are filled into seven soil storerooms connected in turn.After evaluation,the variation in content of fine sand(ΔR_(f))and the hydraulic conductivity of soils in each storeroom(C_(i))are analyzed.In the non-loss test,the soil sample filling area is divided into runoff,transited,and accumulated areas according to the negative or positive ΔR_(f) values.ΔR_(f) increases from negative to positive along the seepage path,and Ci decreases from runoff area to transited area and then rebounds in accumulated area.In the soil-loss test,all soil sample filling areas belong to the runoff area,where the gentle-loss,strengthened-loss,and alleviated-loss parts are further divided.ΔR_(f) decreases from the gentle-loss part to the strengthened-loss part and then rebounds in the alleviated-loss part,and C_(i) increases and then decreases along the seepage path.The relationship between ΔR_(f) and Ci is different with the boundary condition.Ci exponentially decreases with ΔR_(f) in the non-loss test and increases with ΔR_(f) generally in the soil-loss test.

关键词： Suffusion Permeability Experimental investigation Boundary effect Horizontal seepage

Experimental investigation for Co-Combustion Characteristics of Semi-Coke and Bituminous Coal in a 3 MWth Tangential Combustion Facility

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Journal of Thermal Science 2020年第6期29卷 1655-1662页

作者： GUAN Jingyu YU Qiang SUN Rui SHEN Tao WANG Minghao YAN Yanfei SONG Xin School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China State Key Laboratory of Efficient and Clean Coal-Fired Utility Boilers Harbin Boiler Company LimitedHarbin 150046China

An Experimental investigation was conducted in a 3 MW pilot-scale tangential combustion facility to explore the co-combustion characteristics of bituminous coal mixed with semi-coke.The thermal gravimetric analyzer(TGA)was used to obtained fuel thermal analysis.The results presented effects of semi-coke blending ratio(BR)on average furnace temperature,ignition temperature,NO emission and combustion efficiency.The excess air coefficient in main combustion sections and outlet were fixed at 0.85 and 1.2 while BR increased from 0%to 50 wt.%.The temperature profiles of combustion decreases along the height of furnace while average furnace temperature fluctuates slightly with an increasing BR.The concentration of NO has an increasing tendency with the increasing of BR.The ignition temperature obtained from TGA measurement agreed well with experiment result.In addition,combustion efficiency was not sensitive to BR and decreased slightly with the increasing BR.

关键词： tangential combustion semi-coke blending ratio combustion characteristics Experimental investigation