Small-scale fire tests in the underwater tunnel section model with new sidewall smoke extraction

The Shenzhen–Zhongshan Bridge is a 24‐km‐long bridge and tunnel system,including a 6.8-km-long super cross section subsea tunnel.To solve the smoke exhaust problem of a super large cross-section subsea tunnel,the tunnel has a new smoke exhaust system that combines a horizontal smoke exhaust cross section at the top and sidewall smoke exhaust holes.In order to evaluate the potential fire hazards of this type of tunnel,a 1:30 tunnel model was established and 140 smallscale experiments on underwater tunnel fires were conducted.By changing the fire power,fire location,and fan operation mode,different scenarios of submarine immersed tunnel fire were simulated and the related key parameters such as fire smoke diffusion behavior and smoke temperature distribution were studied.On this basis,the optimal smoke control strategy was proposed for different fire scenarios.The research results indicate that the new smoke exhaust system can fully utilize the smoke flow characteristics,significantly improve smoke exhaust efficiency,and increase available evacuation time,thus further enhancing the fire safety of super large cross-section subsea tunnels.

31.38 Gb/s GaN-based LED array visible light communication system enhanced with V-pit and sidewall quantum well structure

Although the 5G wireless network has made significant advances,it is not enough to accommodate the rapidly rising requirement for broader bandwidth in post-5G and 6G eras.As a result,emerging technologies in higher frequencies including visible light communication(VLC),are becoming a hot topic.In particular,LED-based VLC is foreseen as a key enabler for achieving data rates at the Tb/s level in indoor scenarios using multi-color LED arrays with wavelength division multiplexing(WDM)technology.This paper proposes an optimized multi-color LED array chip for high-speed VLC systems.Its long-wavelength GaN-based LED units are remarkably enhanced by V-pit structure in their efficiency,especially in the“yellow gap”region,and it achieves significant improvement in data rate compared with earlier research.This work investigates the V-pit structure and tries to provide insight by introducing a new equivalent circuit model,which provides an explanation of the simulation and experiment results.In the final test using a laboratory communication system,the data rates of eight channels from short to long wavelength are 3.91 Gb/s,3.77 Gb/s,3.67 Gb/s,4.40 Gb/s,3.78 Gb/s,3.18 Gb/s,4.31 Gb/s,and 4.35 Gb/s(31.38 Gb/s in total),with advanced digital signal processing(DSP)techniques including digital equalization technique and bit-power loading discrete multitone(DMT)modulation format.

ANALYSIS OF INTERNAL WAVERIDER INLET AND TYPICAL SIDEWALL COMPRESSION INLET PERFORMANCE

A new internal waverider inlet with a rectangular shape of entrance and exit in front view is designed at Ma=6.0.The design is based on a better basic flowfield ICFC than traditional one and derived with the technology of stream tracing and shock cutting.Comparison between the newly designed inlet and a typical sidewall compression inlet is given.The design Mach number and entrance shape of this new inlet are chosen according to the sidewall compression inlet.Numerical results show that most of the performance parameters of the internal waverider inlet are a bit higher than the sidewall inlet,such as the flow capture coefficient,total pressure recovery and the kinetic efficiency.The performances of these two inlets at off-design points are compared.The internal waverider inlet can capture more than 91% of incoming flow under all simulated conditions.Results show that internal waverider inlet using 3-D compression and high flow capture coefficient is a kind of fixed-geometry inlet with better performance.

Experimental study on thermal environment in large-space building with low sidewall air supply

The thermal environmental characteristics are experim-entally studied in terms of different air supply volumes and outdoor meteorological parameters in a large-space building which is air conditioned with a low sidewall air supply.The experimental results show that the indoor vertical temperature distributions under different condition are similar.The maximum vertical temperature difference（MVTD）is up to about 20 ℃,and it linearly changes with the sol-air temperature.The indoor vertical temperature gradients（VTGs）in the upper,central and lower zones are different.The influence of the sol-air temperature on the VTGs in the upper and the lower zones is greater than that in the central zone.The characteristics of the VTGs in the three zones affected by the air supply volume are the same as those affected by the sol-air temperature.Besides,because of the small air velocity,the predicted mean vote（PMV）on comfort in the occupied zone is slightly high and the air temperature difference between the head and the ankle is usually more than 3 ℃.

Thermal stratification level of low sidewall air supply with air-conditioning system in large space

The thermal stratification level of low sidewall air supply system in large space was defined. Depending on the experiment of low sidewall air supply in summer 2008,the thermal stratification level was studied by simulation. Based on the simulation of experiment condition,the air velocity and vertical temperature distribution in a large space were simulated at different air-outlet velocities,and then the thermal stratification level line was obtained. The simulation results well match with the experimental ones and the average relative error is 3.4%. The thermal stratification level is heightened by increasing the air-outlet velocity with low sidewall air supply mode. It is concluded that when air-outlet velocity is 0.29 m/s,which is the experimental case,a uniform thermal environment in the higher occupied zone and a stable stratification level are formed. When the air-outlet velocity is low,such as 0.05 m/s,the thermal stratification level is too low and the air velocity is too small to meet the human thermal comfort in the occupied zone. So,it would be reasonable that the air-outlet velocity may be designed as 0.31 m/s if the height of the occupied zone is 2 m.

A New Arrangement with Nonlinear Sidewalls for Tanker Ship Storage Panels

Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank in these vehicles is partially filled, it is essential to be able to evaluate the fluid dynamic loads on tank perimeter. Different geometric shapes such as rectangular, cylindrical, elliptical, spherical and circular conical have been suggested for ship storage tanks by previous researchers. In this paper a numerical model is developed based on incompressible and inviscid fluid motion for the liquid sloshing phenomenon. The coupled BEM-FEM is used to solve the governing equations and nonlinear free surface boundary conditions. The results are validated for rectangular container using data obtained for a horizontal periodic sway motion. Using the results of this model a new arrangement of trapezoidal shapes with quadratic sidewalls is suggested for tanker ship storage panels. The suggested geometric shape not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing effects more efficiently than the existing geometric shapes.

Effect of Organophilic Montmorillonite on Thermal-oxidative Aging Behavior of SBS Modified Bitumen Crack Filling Material

Styrene-butadiene-styrene （SBS） modified bitumen crack filling material with organophilic montmorillonite （OCFM） was prepared by melt blending. X-ray diffraction analysis shows that the interlayer spacing of organophilic montmorillonite （OMMT） in OCFM is widened and an exfoliated structure may be formed. Thermal-oxidative aging behavior of OCFM and SBS modified bitumen crack filling material （SCFM） was investigated. The experimental results indicate that the rate of thermal-oxidative aging of OCFM is much slower than that of SCFM, which can be attributed to barrier of exfoliated structure of OCFM to oxygen.

Research and application of sidewall stability predic-tion method based on analytic hierarchy process and fuzzy integrative evaluation method

As a difficult problem, sidewall instability has been beset drilling workers all the time. Not only does it cause huge economic losses, but also it determines the success or failure of drilling engineering. Due to complex relationship between various factors which influence sidewall stability, it hasn’t been found a widely applied method to predicate sidewall stability so far. Therefore, in order to formulate corresponding measures to ensure successful drilling, searching for a kind of better method to forecast sidewall stability before drilling becomes an imperative and significant topic for drilling engineering. On the basis of traditional sidewall stability analytical method, we have put forward the Fuzzy Comprehensive Evaluation Method to forecast sidewall stability regulation using physico-chemical performance parameters of the clay mineral. This method has been improved by introducing the Analytic Hierarchy Process (AHP) and the Maximum Subjection Principle in the application process. After introducing Analytic Hierarchy Process to identify weight, and Maximum Subjection Principle to obtain evaluation results, it has reduced the influence of human factors and enhanced the accuracy of the fuzzy evaluation results. The application in Hailaer Area indicates that this method can predict sidewall stability of gas-oil well with high credibility and strong practicability.

Numerical Simulation of PMM Tests for A Ship in Close Proximity to Sidewall and Maneuvering Stability Analysis

As the maneuverability of a ship navigating close to a bank is influenced by the sidewall, the assessment of ship maneuvering stability is important. The hydrodynamic derivatives measured by the planar motion mechanism （PMM） test provide a way to predict the change of ship maneuverability. This paper presents a numerical simulation of PMM model tests with variant distances to a vertical bank by using unsteady RANS equations. A hybrid dynamic mesh technique is developed to realize the mesh configuration and remeshing of dynamic PMM tests when the ship is close to the bank. The proposed method is validated by comparing numerical results with results of PMM tests in a circulating water channel. The first-order hydrodynamic derivatives of the ship are analyzed from the time history of lateral force and yaw moment according to the multiple-run simulating procedure and the variations of hydrodynamic derivatives with the ship-sidewall distance are given. The straight line stability and directional stability are also discussed and stable or unstable zone of proportional-derivative （PD） controller parameters for directional stability is shown, which can be a reference for course keeping operation when sailing near a bank.

Study on mechanical principle of reinforcing sidewalls and corners of roadway to control floor heave by anchors

The movement principle of sidewalls and floor of extraction opening is analyzed, it is found that floor heave not only has something to do with the floor strata, but sidewalls. The effect of sidewall anchor and corner anchor is studied, the mechanical principle of reinforcing sidewalls and corners is put forward and applied in engineering practice.

Experimental Investigation of Flame Structure and Combustion Limit During Premixed Methane/Air Jet Flame and Sidewall Interaction

The effects of inlet gas parameters and sloping sidewall angle on the flame structure and combustion limit with and without sidewall were experimentally investigated.Flame height and impact angle were obtained by chemiluminescence intensity analysis of CH*distribution.First,the combustion characteristics of flame with and without sidewall at different equivalence ratios were explored;then,the influence of Reynolds number and inlet gas temperature on flame structure and combustion limit of v-shaped flame with sidewall were analyzed,and the results with sidewall were compared with those without sidewall.Finally,the variation trend of flame parameters with different sloping sidewall angles was analyzed.The experimental results show that the existence of sidewall makes flame shape change from“M-shaped”to“inverted N-shaped”,and conical shape to trapezoidal shape.The inhibition effect of sidewall on flame stretching downstream is strengthened with the increase in Reynolds number;but as the temperature of the inlet gas increases,the inhibitory effect is obviously weakened.When sloping sidewall angle decreases from 90°to 55°at 5°intervals,flame height and impact angle of v-shaped flame reach the extreme value whenβ=80°.Compared with the case without sidewall,the range of v-shaped flame with sidewall has no obvious trend of broadening or shrinking when inlet gas temperature is increased;however,as sloping sidewall angle decreases,the range of the v-shaped flame shrinks obviously and flammability limit increases significantly.

SIDEWALL FLOW STABILITY IN THE MHD CHANNEL FLOWS

The velocity distribution between two sidewalls is; M-shaped for the MHD channel flows with rectangular cross section and thin conducting walls in a strong transverse magnetic field. Assume that the dimensionless numbers R(m) much less than 1, M, N much greater than 1, and sigma* much less than 1 and that the distance between two perpendicular walls is very long in comparison with the distance between two sidewalls. First, the equation for steady flow is established, and the solution of M-shaped velocity distribution is given. Then, an equation for stability of small disturbances is derived based on the velocity distribution obtained. Finally, it is proved that the stability equation for sidewall how can be transformed into the famous Orr-Sommerfeld equation, in addition, the following theorems are also proved, namely, the analogy theorem, the generalized Rayleigh's theorem, the generalized Fjortoft's theorem and the generalized Joseph's theorems.

高温小井眼大直径岩心旋转井壁取心仪研制及应用

随着油气勘探开发难度增大,特别是海洋油气勘探开发的不断加大,以及深水井、高温井越来越多,地质方面对电缆测井技术所获取的参数要求也越来越高。为了更好地获取小井眼尺寸井壁岩心样本,助力油气田高效探勘开发,通过对取心仪井下仪器关键零部件电子控制短节和机械液压短节的创新设计与模拟分析,研制了适用于高温、高压、小尺寸井眼的大直径旋转井壁取心仪(MRCT-dumpy)。通过功能测试和5口井作业应用表明,大直径旋转井壁取心仪钻头性能及取心电机性能均得到充分验证,其热管理系统满足作业需要,符合设计要求;该取心仪取心功能正常,最高单趟收获岩心43颗,满足小井眼大直径取心作业要求。该仪器的设计与应用可为后期同类技术的发展提供指导。

基于电弧声信号的窄间隙脉冲熔化极气体保护焊侧壁熔合状态在线识别

为在焊接过程中实时了解焊缝内部的焊接状况,构建了电弧声信号实时采集系统。在焊枪摆动中心处于不同位置的情况下,进行了电弧声信号特征与侧壁熔合状态的相关性分析。分别从时域与频域中提取了与侧壁熔合状态相关性较强的电弧声特征。为进一步提高熔合状态预测的有效性,采用电弧声特征参量构建了支持向量回归的侧壁熔合状态识别模型。为减小不良特征对识别模型的影响,显著提高模型的识别精度,采用遗传算法进行了参数寻优。参数寻优后模型的总体识别率达93.33%,实现了窄间隙侧壁熔合状态的有效识别。

高应力扇形中深孔采场边帮控制爆破参数优化

针对扇形孔采场爆破边帮控制问题,提出了一种将靠近边帮的扇形炮孔施工成垂直平行孔用以控制边帮的构想。首先,通过理论计算得到4组平行炮孔不耦合系数与炮孔间距匹配下的模型参数,使用LS-DYNA对4组参数进行数值模拟;然后,通过对比分析4组模型在无地应力作用和不同方向地应力作用时的爆破裂纹扩展情况,获得最优参数;最后基于优化参数开展工业试验。结果表明:高地应力会促进最大应力方向爆破裂纹扩展;4种模型中,不耦合系数为1.65,炮孔间距为1.1 m时开挖区域破岩效果最为合理;在试验采场开展工业试验,使用优化后的爆破参数进行爆破,采场回采后边帮平整,稳定性较好,验证了研究结论的正确性。

上海软黏土的非水相有机液体固结渗透仪渗透试验

在饱和黏性土的非水相有机液体(NAPL)渗透试验中,NAPL-土的相互作用易导致土样收缩而产生侧壁渗漏,影响试验结果的可靠性。采用固结渗透仪开展了上海淤泥质黏土的煤油渗透试验,研究竖向固结压力pv的大小和土样结构性对侧壁渗漏以及试验结果的影响。研究结果表明,絮凝结构的原状土样在pv为50 kPa、200 kPa下均存在侧壁渗漏,测得的渗透系数偏大,在pv=400 kPa下可得到可靠的试验结果。对于分散结构的重塑土,在pv=400 kPa下仍然存在侧壁渗漏。根据原状土样的孔径分布以及在pv=400 kPa下的渗透试验结果,讨论了上海淤泥质黏土中NAPL渗透的基本特性,对了解沿海软黏土中NAPL类污染物的迁移特征有指导价值。

侧开竖井曲线隧道烟气运移规律及排烟效果影响因素研究

城市侧壁开口竖井隧道火灾烟气流动规律复杂,通过FDS数值模拟,分析了曲率半径、竖井侧壁开口尺寸、纵向风速3个因素对火灾烟气运移规律及竖井排烟效果的影响,并采用正交试验判断各因素的重要程度。结果表明:曲线隧道烟气的沉降速度更快,当烟气层未完全覆盖竖井侧壁排烟口时排烟口长度大于临界值后竖井下游顶棚温度衰减系数才逐渐增加;纵向风速对直线和曲线隧道的烟气逆流长度、临界风速及排烟效果的影响差异较大,提高侧壁开口竖井排烟效率存在最优风速,但会使竖井与主隧道衔接处平均温度提升20%,最高温度位于联通管道下游侧。影响排烟效率的各因素重要程度为:纵向风速>竖井侧壁开口尺寸>曲率半径,影响顶棚下方平均温度的重要程度为:纵向风速>曲率半径>竖井侧壁开口尺寸。

渤海海域井壁取心裂解烃S_(2)烃类损失恢复回归分析

地化录井受工程、地质条件及人为因素的影响,往往造成岩石样品从井底到地表的烃类损失,不能很好地反映地下储层的真实含油气信息,因此需要一种合理准确的方法进行烃类损失恢复。针对渤海海域不同地区不同层位的岩屑值(自变量)与壁心值(因变量)之间的关系,基于最小二乘法、梯度下降法及其衍生算法,以多元线性回归和非线性回归两种方式来拟合研究区井壁取心数据。多元线性回归模型可使用标准方程法、岭回归、LASSO(Least Absolute Shrinkage and Selection Operator)及弹性网进行回归拟合,非线性回归模型可使用梯度下降法和分段函数的拟合方法。对不同回归分析方法进行分析对比可知,岭回归在计算线性关系的烃类损失方面具有较好的效果,决定系数r^(2)均超过0.7;基于岭回归分段函数拟合和非线性回归模型y=x/(b+kx)适合非线性烃类损失恢复。与传统的烃类损失恢复方法相比,使用量化的方式对研究区烃类进行恢复,更加科学全面,具有广泛的应用前景。

浅埋隧道双侧壁导坑法施工数值模拟研究

为准确评价浅埋隧道施工过程的围岩稳定性,利用ANSYS有限元数值分析软件,对沈阳地铁10号线区间浅埋隧道双侧壁导坑法施工进行数值模拟,研究了浅埋隧道施工过程的力学特性及变形规律。结果表明:开挖中上导洞后,围岩位移、应力和支护结构内力显著增大,占整个导洞开挖的50%,且最大位移、应力和支护结构弯矩集中在拱顶、初期支护连接的薄弱处;地表沉降量随时间变化增长趋缓,开挖90 d后趋于稳定,且离开挖面越近,沉降量越大,最大沉降点出现在最先开挖的中上导洞位置;隧道开挖10 d内拱顶下沉较快,随开挖掌子面远离监测点,拱顶沉降速率逐渐减小,开挖顺序对拱顶沉降影响较大,往往先开挖的位置拱顶沉降最大。现场监测结果表明:数值计算与现场监测结果比较吻合,验证了数值分析的合理性。研究成果对浅埋隧道的安全、经济施工具有借鉴意义。

MEMS矢量水听器敏感结构的后CMOS释放工艺研究

纤毛式微机电系统(MEMS)矢量水听器可探测水下质点振速等矢量信息,与互补金属氧化物半导体(CMOS)集成能够很大程度地提升其性能。针对纤毛式MEMS矢量水听器的CMOS集成提出了一种方案,该方案在MEMS后处理工艺中,利用侧墙保护和各向异性湿法腐蚀从正面释放水听器的十字梁敏感结构。整个后处理过程不需要光刻,降低加工难度的同时,保证了加工结构的精确性。设计出了一种验证性的工艺流程,具体分析了4种不同结构的湿法腐蚀过程。最终完成了这4种结构的工艺流片,对实验结果进行了分析。实验验证了该方案的可行性,为纤毛式MEMS矢量水听器的CMOS集成奠定了基础。