A numerical study of vortex interactions with flames developing from ignition kernels in lean methane/air mixtures

In this work, the outcomes of interactions of counter-rotating vortex pairs with developing ignition kernels are studied. The conditions are selected to represent those in a lean-burn natural-gas engine with hot-jet ignition. The evolution of flame surface area during kernel–vortex interaction is quantitatively and qualitatively examined. It is observed that flame development is accelerated and the net flame surface area growth rate, i.e. heat release rate, increased with increasing vortex velocity. In general, increasing the vortex length scale increases the surface growth rate, i.e. increases heat release rates, but for small length scales, i.e. when the ratio of vortex length scale to kernel diameter is small, high flame curvature induced during the interaction leads to flame weakening and slower growth rates. When the vortex velocity is high relative to the flame speed and the length scale is comparable to the kernel diameter, the vortex breaks through the ignition kernel carrying with it hot products of combustion. This accelerates growth of the flame surface area and heat release rates compared to a kernel with no vortex interaction. On decreasing the vortex velocity and increasing the length scale, the wrinkling of the kernel becomes important. This also results in increased surface growth rates and higher heat release rates.     

Study on the critical submergence of surface vortices and the design of anti-vortex intakes

Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of ‘critical spherical sink surface’(CSSS).The vortex formation and evolution at the tunnel intake were analyzed based on the theory of CSSS considering the effect of circulation.A theory was proposed to explain the surface vortex.The theoretical development was verified by the physical model experiments of Xiluodu hydropower station.The radial velocity a...     

Flux Enhancement in a Helical Microfiltration Module with Gas Injection

Abstract

A helical flow module with an inner rod mounted membrane was designed and built to reduce gel layer deposit and membrane fouling during microfiltration. Controlled centrifugal instabilities resulting from flow in a helically grooved channel, as well as the leakage flow between adjacent grooves, generated secondary vortex flows. The permeation fluxes for helical modules with Dean vortex flow were compared with flat crossflow modules at different operating pressures, concentrations, and feed flow rates. The permeation flux of the helical module for a feed solution containing 0.3 wt% kaolin solution at 1.2 bar was 57% higher than that of the flat module. Moreover, in addition to secondary vortex flow, compressed air was introduced to the membrane module. The increase in flux for the helical module with air injection was significant: the flux enhancements at 1.3 bar, 2 L‐solution/min and 1.3 L‐air/min for 0.1 wt% solutions of kaolin and bentonite were 47 and 73%, respectively.     

涡压挤扩机理应用于地基处理的室内试验研究

分析了现有各种地基处理方法的优缺点,首次提出并经室内试验验证了涡压挤扩机理。使用自行设计制作的涡压挤扩环境箱和钢套管实施粘性土和砂性土的涡压挤扩试验,设置于钢套管内的涡压叶片可顺利地将其内部的流态混凝土挤扩到周围的土体中。定义了扩径比,测得不同扭矩条件下砂性土和粘性土的扩径比,并得到其极限扭矩。对涡压过程中混凝土可能出现的流动形态进行分析,建立混凝土流动分析模型,得到流态混凝土在涡压腔内的动力学模型。结果表明,采用涡压挤扩方法处理地基在理论上是可行的,具有较强的适用性,涡压挤扩方法将为地基处理行业注入新的活力。     

受油机扰动特性的建模与仿真

针对紧密编队飞行过程中产生的尾涡流场对空中加油机产生扰动影响的问题,建立了受油机扰动运动模型。将风扰动主要分解为大气紊流和加油机尾涡,分别建立工程化的Dryden大气紊流模型和尾涡模型,将叠加的2个扰动加入到受油机的非线性刚体运动方程中,并对受油机扰动运动进行仿真分析。仿真结果表明：该叠加的方法能够简单有效地模拟反映复杂的气流扰动,为进一步研究空中加油控制系统提供参考。     

涡街流量计的研究

涡街流量计是目前发展势头十分良好的流量计,在管道流量测量中得到广泛应用,并已跻身通用流量计之列.但涡街流量计尚属发展中流量计,其理论基础和实践经验较薄弱,在使用中,还会出现一些预想不到的问题.为解决这些问题,国内外科研工作者进行了大量的研究工作,并取得了一定进展.从涡街流量计中旋涡分离、涡街发生体形状、涡街信号检测方法及涡街信号分析和处理几方面对国内外研究现状进行了综述,指出研究中存在的难点及今后的研究方向,并提出一种利用涡街原理的新质量流量测量方法.     

CFD模拟旋风分离器自然旋风长

利用计算流体力学软件Flowizard对不同结构尺寸的旋风分离器气相流场进行数值模拟采用分离器锥体段中心湍动能峰值定位自然旋风长的方法，分析了入口面积、芯管下口直径、下溢口直径和锥体段长度对自然旋风长的影响。拓展了分离器内部流场由多个自然转折旋风串联的概念。通过增加锥体段长度和入口风速来实现旋风串联、多级分离的效果，延长自然旋风长，有益于提高分离效率。     

对太子河流域煤田西部构造的认识

太子河流域煤田西部区（如本溪煤田和红阳煤田）为旋卷构造和伸展构造所控制；受太平洋板块对大陆边缘俯冲和大陆的仰冲先后产生旋扭和拉张形成上述两种构造类型，形成时间为晚侏罗世至早第三纪。     

旋浮熔炼+旋浮吹炼与富氧侧吹熔炼+多枪顶吹连续吹炼工艺比较

简要介绍了旋浮熔炼+旋浮吹炼与富氧侧吹熔炼+多枪顶吹连续吹炼工艺流程,通过对比分析这两种工艺的生产技术指标、造渣熔剂消耗、冶炼能耗和杂质元素适应性,阐明了它们各自的工艺特点,为我国后续新建或升级改造铜冶炼项目的工艺选择提供参考。     

基于风洞试验及大涡模拟的宽体扁平箱梁涡振特性研究与优化

基于1∶60节段模型风洞试验,研究了桥面附属构件对宽高比为12的宽体扁平箱梁涡激振动性能的影响。研究发现,成桥态主梁在正攻角(+5°,+3°)下发生了显著的竖弯和扭转涡振,而提高人行护栏透风率或内移检修车轨道均可同时降低两种涡振的振幅,且提高人行护栏透风率还可缩短两种涡振的风速锁定区范围。采用三维大涡模拟(3D LES)进行了施工态和成桥态的静态绕流计算,发现不合理附属构件将使箱梁上下表面均形成大范围流动分离,在迎风侧人行护栏、两道检修车轨道三处分离点产生的漩涡各自以不同频率向尾流脱落,从而诱发较强的涡振响应。