Power Density and Electrical Efficiency in Closed Cycle MHD Generator with Fully Ionized Seed

Effects of a reduced seed concentration on performances of a nonequilibrium MHD generator are investigated by calculating power densities and electrical efficiencies for both Faraday and Hall generators.

It is shown that high electrical efficiencies and high power densities are obtained simultaneously by suppressing the ionization instability with reduced seed fractions (10^?4 ～10^?5) when values of the effective electrical conductivity and the effective Hall parameter recover to above 50% of their ideal ones. Results also indicate that argon is more suitable for a working fluid than helium in the case of a reduced seed concentration.     

大光包滑坡滑带碎裂岩体原位钻孔剪切试验研究

安县大光包滑坡是汶川地震触发的最大规模滑坡,滑坡南侧暴露长约1.8 km顺层滑带,其岩体高度碎裂化,引起广泛关注。为准确评价滑带碎裂岩体的强度参数,笔者在前人研究的基础上开展了细致的野外调查工作,采用法国Phicometre岩土两用原位钻孔剪切试验仪对大光包滑坡滑带碎裂岩体进行了原位剪切试验。将试验结果与Hoek–Brown岩体强度准则估值和基于工程地质类比法的力学参数建议值进行了对比分析。基于以上研究,提出了大光包滑坡南侧顺层滑带碎裂岩体力学参数建议值:内聚力为245~480 k Pa,内摩擦角为25.0°~26.5°。     

Composite hydrogeological investigation and characterisation methods applied at a nuclear power plant site in Taiwan

Drawing from the lessons learnt from the Fukushima nuclear disaster in Japan, the assessment of subsurface environmental hazard around nuclear power plants has emerged as a critical task. Consequently, aiming to better understand the possible environmental impact of radiation leaks into the groundwater, a prescreening programme was initiated in 2011 by the Taiwanese government. As part of this programme, this study conducted various borehole prospecting techniques to identify in situ hydrogeological characteristics at Chin‐Shan Nuclear Power Plant. Borehole electrical log, sonic log and temperature/conductivity log were conducted to explain the regional lithologic conditions and permeability of the formation. In conjunction with this, the interwell tracer and pumping test was carried out to simultaneously determine the hydraulic parameters. In our opinion, the implementation of such in situ end‐to‐end investigations is essential in interpreting in situ fluid and solute transport dynamics prior to programming any numerical scheme for early warning, vulnerability assessment and regular monitoring of a nuclear power plant site.     

Experimental study of the effects of hydrogen addition on the thermoacoustic instability in a variable-length combustor

The current study examined the self-excited thermoacoustic instability of hydrogen/methane premixed flames using a variable-length combustor (300–1100 mm). The global dynamic pressure, heat release rate oscillation, together with the flame dynamics were studied. Results showed that both the hydrogen concentration and the chamber length were critical in determining the acoustic oscillation mode and instability trend. Low-frequency primary acoustic modes (<200 Hz) were mainly excited when the hydrogen concentration was low, whereas primary acoustic modes with relatively higher frequencies (~400 Hz) tended to occur in cases with a high hydrogen proportion (>40%). For primary acoustic modes lower than 200 Hz, the primary oscillation frequency tended to increase linearly with a rising hydrogen proportion. Heat release oscillation and flame dynamics analyses demonstrated that for the flame with large-scale shape deformation, the initial addition of hydrogen would intensify the heat release oscillation. Nevertheless, a further increase in the hydrogen level tended to inhibit the heat release oscillation by weakening the flame shape deformation. Eventually, a sufficient high-level of hydrogen addition would weaken the primary acoustic modes that have similar frequencies.     

基于“三带”理论的沉陷区边坡失稳过程分析

地下开采扰动给沉陷区内边坡稳定性带来不利影响。以抚顺老虎台矿开采沉陷区内某边坡失稳破坏为例，分析沉陷区内边坡失稳的动态演化过程。根据开采沉陷学“三带”理论，将处于开采沉陷区的东露天边坡岩土体划分为冒落带、裂隙带、弯曲下沉带和原生带4个特征区域,并分别计算出边坡处于3种“临界状态”时对应的地下开采深度。     

盐卤水平井对接连通技术在长宁盐矿的应用

随着水平钻井技术的发展和完善,对接连通法开采方式已成为目前国内外盐矿开发最有效的技术手段。长宁盐矿盐卤水平井对接连通的成功实施不仅为盐卤、石油开采,而且为其他流体矿藏的开采提供了一条新的途径。     

浅谈灌注桩成孔质量检测中存在的问题

根据对灌注桩试成孔的检测,从而评价场地地层情况与勘察结果是否吻合,所选择设备、机具及施工工艺和参数是否合理;以及对试成孔检测本身存在的问题提出笔者的分析,从而更好地控制灌注桩质量,为工程服务。     

3.705 μm紧凑型光参量振荡器

报道了一种基于工程应用的3.705 μm紧凑型高稳定性光参量振荡器。采用半导体制冷、强制气体对流冷却和热管导热技术相结合的方式,对主振荡功率放大结构的掺Yb光纤泵浦模块泵浦过程中产生的废热进行有效管理,再将经过耦合后的泵浦光注入到使用温控炉精确控温的PPMgLN晶体,在重复频率为55.56 kHz时,获得了功率不稳定度优于1.5%的1.78 W,脉冲宽度120 ns,峰值波长3.705 μm的线偏中红外激光输出,光光转换效率为12.6%。     

Flame morphology and self-acceleration of syngas spherically expanding flames

The self-acceleration of spherically expanding flames were investigated using a constant volume combustion chamber for CO/H₂/O₂/N₂ mixtures over a wide range of initial pressure from 0.2 to 0.6 MPa, CO/H₂ ratio from 50/50 to 10/90 and equivalence ratio from 0.4 to 1.5. The adiabatic flame temperature was kept constant by adjusting O₂/N₂ ratio at different equivalence ratios. Schlieren images were recorded to investigate the flame front evolution of spherically expanding flames. Local acceleration exponents were extracted using a proper equation to study the process of flame self-acceleration. Results show that the flame cells develop on the smooth flame fronts and finally reach fractal-like structures due to the hydrodynamic and diffusional-thermal instabilities, resulting in flame self-accelerative propagation. The critical Peclet number corresponding to the onset of self-acceleration, Pe_cr increases nonlinearly with the Markstein length, Ma. The observation further reveals that the onset of self-acceleration is mainly controlled by the diffusional-thermal effect. There exists two distinct flame propagation regimes in the self-acceleration, namely quick transition accelerative and quasi self-similar accelerative regimes. The quick transition regime is controlled by the destabilization effect of hydrodynamic perturbation and stabilization effect of flame stretch. While the quasi self-similar regime is primarily affected by the cascading process of flame front cells controlled by hydrodynamic instability. The self-similar acceleration exponent, α_s varies with the initial pressure and Lewis number, Le. The values of α_s are measured to be 1.1–1.25 (smaller than 1.5), indicating the flame dose not attain self-turbulization.