空气反循环钻探探头空间流场分析及其影响因素研究

空气反循环技术因其具有上返流量可调、安全等特点,在海洋钻探中有巨大的应用前景。但在海洋环境中,受喷射孔导流作用以及孔底复杂狭窄空腔影响,能否顺利实现气路反循环效应是该技术能否实现应用的关键,因此对空气反循环钻探探头空间气体流场分析是十分必要的。本文基于计算流体动力学理论,借助FLUENT软件,对探头周围空间气体流场进行数值模拟,分析空气入口数量、出射孔数量、空气入口与引射孔的相对位置以及引射孔数量等因素对空气反循环钻探探头性能的影响,研究结果显示,空气入口数为2,出射孔数量为4,空气入口与引射孔交错排列,引射孔数量为4的方案下引射效果最优。上述结论为进一步研究各参数之间的耦合关系对引射效果的影响打下基础。Air reverse circulation technology has great application prospects in offshore drilling because of its features such as adjustable upflow rate and safety. However, in the Marine environment, due to the effect of jet hole diversion and the complex narrow cavity at the bottom of the hole, whether the air path can successfully achieve reverse circulation is the key to the successful design, so it is very necessary to analyze the space flow field of the air reverse circulation drilling probe. Based on the theory of computational fluid dynamics and FLUENT software, this paper numerically simulates the spatial flow field around the probe, and analyzes the effects of factors such as the number of air intakes, the number of perforations, the relative positions of air intakes and perforations, and the number of perforations on the performance of the probe for air reverse circulation drilling. The research results show that the number of air intakes is 2 and the number of perforations is 4. The air inlet and injection holes are staggered, and the injection effect is the best when the number of injection holes is 4. The above research lays a foundation for further study of the coupling relationship between the parameters.

基于CFD的非道路车辆尾气后处理器性能研究

本文针对一款非道路柴油机的尾气后处理装置进行了仿真和实验研究。应用计算流体力学软件建立了尿素溶液的喷射、液滴雾化以及蒸发模型,液滴与固体壁面相互作用模型。研究了一种基本型系统的SCR系统对尿素液滴雾化、蒸发和分解及SCR催化剂载体入口NH3分布均匀性、烟气速度均匀性、压力损失、液膜分布的影响。数值计算结果显示,该系统的结构紧凑化设计(短系统)后在烟气速度均匀性、氨气浓度均匀性、系统总压损失方面均满足设计要求;基于对液膜分布与累积量的计算和评价,短系统的抗结晶性能好于长系统,具备相对更高的系统耐久性能。同时,设计了一组稳态发动机台架结晶对比实验,台架试验得出了与仿真相一致的结晶趋势,短方案抗结晶能力强于长方案,另一方面也验证了CFD手段在系统结晶风险预测上的有效性。