海洋天然气水合物层钻水平井不同扩径方式携岩能力图版

我国海洋天然气水合物具有埋深浅、层薄、欠压实、弱胶结的成藏特点,长水平井可能是未来商业化开发的有效模式。然而在海洋天然气水合物层钻水平井过程中,由于水合物层欠压实、弱胶结岩石力学强度极低且含水合物的岩屑颗粒会在其重力作用下沉积,造成携岩不畅,从而增大钻具摩阻、扭矩并制约水平井眼的延伸能力。为此,建立了直角扩径、45°斜角扩径、圆弧扩径3种不同扩径方式模型,并用EDEM和FLUENT进行耦合仿真得到了携岩所需临界流速理论图版。仿真研究结果表明:在3种不同扩径方式下,水合物丰度一定时,随着含水合物的岩屑颗粒增大,携岩所需临界流速增大,随着钻井液密度增大,携岩所需临界流速减小;钻井液密度一定时,随着水合物丰度增大,携岩所需临界流速减小;水合物丰度和钻井液密度一定时,直角扩径方式的携岩能力最差,45°斜角扩径方式携岩能力中等,圆弧扩径方式的携岩能力最强。研究结果为海洋天然气水合物藏水平井开采模式的施工参数优化提供了前期技术支撑。

扩径导线的分类与扩径方式的选择

扩径导线主要用在特高压线路、高海拔地区、人口密集的地区。介绍了国内外扩径导线的应用情况和针对"皖电东送"淮南—上海输变电工程线路研制的2类扩径导线。通过分析现有的扩径导线的特点,提出了扩径导线的分类方式:按用途分为线路用和变电站用2大类;按结构特点分为大内径铝管支撑型扩径导线、小内径铝管填充型扩径导线、疏绞型扩径导线、高密度聚乙烯支撑型扩径导线。在总结研发经验的基础上,提出了选择扩径方式的原则性意见。

Influence of various volute designs on volute overall performance

This paper discusses the influence of various volute designs on volute overall performance for a certain centrifu- gal compressor with both vaned and vaneless diffuser. Firstly, based on a free vortex flow pattern and the assumption of a circumferentially uniform flow at the design condition, a corrected method for volute design is adopted. By means of this method, corresponding to five geometric parameters affecting the volute overall performance, ten volute cases are designed. Secondly, the numerical simulation is employed and the detailed flow field and losses in different volutes with different geometric parameters are analyzed. The numerical investigation reveals that in all of the five geometric parameters, the radial location of the cross-section has the strongest influence on the performance of the volute. The non-uniform volute inlet formed by the upward vaned diffuser outlet flow is another important factor. Finally a relatively better value of D1/D2 is concluded.