Numerical analysis of the two-phase pressure drop and liquid distribution in single-screw expander prototype

In this paper, the numerical simulations have been carried out to evaluate the two-phase pressure drop and liquid distribution in screw channel. The numerical models are validated against the present experimental data with statistical accuracy. The effects of pitch circle diameter （PCD）, inlet velocity and inlet sectional liquid holdup on the pressure drop and liquid distribution characteristics in the screw channel are illustrated. It is found that decreasing the PCD and increasing the inlet sectional liquid holdup can increase the liquid holdup on the outer side in screw channel. The PCD and the inlet sectional liquid holdup need to be considered in evaluating the two-phase frictional pressure drop per unit length in the screw channel. The PCD has an effect on the development of the average pressure in the various cross sections, and the inlet sectional liquid holdup has no visible impact on the changing process of the pressure drop in the screw channel. The correlation developed predicts the two-phase frictional pressure drop in the screw channel with great statistical accuracy.     

Pressure gradient evolution in the near-Earth magnetotail at the arrival of BBFs

Using in situ observations from THEMIS A, D and E during the 2008-2011 tail season, we present a statistical study of the evolution of pressure gradients in the near-Earth tail during bursty bulk flow （BBF） convection. We identified 138 substorm BBFs and 2,197 non-substorm BBFs for this study. We found that both the pressure and the Bz component of the magnetic field were enhanced at the arrival of BBFs at the spacecraft locations. We suggest that the increase of Bz during non-substorm BBFs is associated with flux pile-up. However, the much stronger enhancement of Bz during substorm BBFs implies the occurrence of magnetic field dipolarization which is caused by both the flux pile-up process and near-Earth current disruption. Furthermore, a bow-wave-like high pressure appears to be formed at the arrival of substorm BBFs, which is responsible for the formation of region-1-sense FACs. The azimuthal pressure gradient associated with the arrival of substorm BBFs lasts for about 5 min. The enhanced pressure gradient associated with the bow wave is caused by the braking and diversion of the Earthward flow in the inner plasma sheet. The results from this statistical study suggest that the braking and azimuthal diversion of BBFs may commonly create azimuthal pressure gradients, which are related to the forrnation of the FAC of the substorm current wedge.     

PCCP管道的水压试验技术分析

给水管道水压试验是对给水管道施工质量的综合性检验,也是管道工程施工的一个重要工序。当PCCP管路安装技术检查资料完整且逐个接口水压试验已合格后,是否进行全线或分段水压试验,我国尚无标准。在内蒙古呼市的引黄一、二期工程、宁夏宁东引水工程中,管材均为PCCP管,管径为DN2200～DN600,业主首次使用PCCP管材,也无PCCP管道水压试验的技术数据,因此要求施工方对管线进行抽检。现将抽检段管道水压试验进行总结,对试验结果进行分析,以便为今后的施工积累经验。     

航空发动机压比控制系统设计及仿真研究

建立了航空发动机喷口-压比线性模型和喷口执行机构数学模型,在此基础上对航空发动机压比控制系统展开研究,设计了三个回路的控制方式。对分油活门位移和作动筒活塞位移分别设计了PI控制和比例控制的内闭环,针对压比采用PID控制,并分别整定了各控制器的参数。仿真表明,该压比闭环控制系统在包线内控制压比效果良好,控制系统鲁棒性强。     

压力成型及添加粘结剂对煤炭破碎性能的影响

本文使用哈氏可磨性测定仪，借用格鲁布斯检验法，通过对比相同粒度级煤炭颗粒的质量来判定压力成型及添加粘结剂对煤炭破碎性能的影响。试验结果表明，压力成型以及添加自制粘结剂均不会影响煤炭的破碎性能。     

李嘴孜矿孔集井-140mA1工作面煤炭自燃防控实践

本文介绍了在预防李嘴孜矿孔集井-140mA1工作面煤炭自燃的过程中,通过采用预埋热电偶、指标气体预测、均压技术、灌浆封堵一系列的预测、预报和预防措施有效的防止了该工作面在掘进和回采期间煤炭自燃。保证了该工作面的安全回采。从而为预防自然发火煤层提供方法指导。     

杉木树煤矿切顶卸压沿空成巷无煤柱开采技术应用研究

结合杉木树煤矿B4上保护层煤层地质情况,进行切顶卸压沿空成巷无煤柱开采技术应用研究,通过反复现场工业性试验,对聚能爆破相关参数、聚能装置安装方式等进行优化,形成了适合杉木树煤矿地质条件的沿空切顶成巷技术.通过研究,解决了杉木树煤矿万吨掘进率高、采掘接续紧张、保护层开采速度慢等问题,提高了矿井资源回收率.     

断块油藏平面动用均衡程度实验研究

为探究断块油藏高含水期平面不均衡动用规律,以指导剩余油的进一步有效挖潜,利用人造三维胶结物理模型研究了倾斜断块油藏不同构造部位生产动态、压力及压力降分布情况。结果表明:模型见水时间较快,见水后含水率迅速上升;但不同构造部位井的见水时间差异较大,是导致平面不均衡驱替的因素之一;对比不同构造部位模型压力的分布,腰部的压力和动用程度分布差异较大,从宏观上看腰部平面不均衡动用程度严重。在生产调整中,需要利用注采耦合、产液量调整等措施保证腰部动用的均衡程度。     

漏失压力研究现状

本文介绍了井漏、井漏的原因及现象,总结和分析了国内外对漏失压力的研究现状,并提出加大漏失压力理论研究力度,尽快得出准确有效的漏失压力计算模型,便于更高效地指导现场防漏堵漏。     

辐射板对磁致伸缩换能器输出特性的影响

辐射板作为磁致伸缩换能器的最终输出元件,它所选用的材料、尺寸、形状将直接影响换能器的工作特性。本文在换能器工作原理的基础上,通过有限元软件ATILA模拟仿真在相同激励力、边界条件下,不同材料、尺寸、形状的辐射板对磁致伸缩换能器输出特性(频率、振动幅值、声压幅值)的影响。结果表明:硬铝材料辐射板出现活塞振型时振幅最大;增加辐射板直径D可有效增加辐射板振动幅值,同时增加辐射板辐射声压值,增加辐射板厚度H可有效增加辐射板出现活塞振型的频率值;凹球面辐射板出现活塞振型时振幅最大,对应谐振腔中声压幅值最高。以上分析结果为合理设计辐射板结构提供了参考。