FCC沉降器粗旋风分离器的料腿泄气率

在粗旋冷态模型实验基础上,采用FLUENT 6.2流体力学计算软件对FCC沉降器粗旋内部的两相流动进行数值模拟,针对稀、密相流动分别采用颗粒随机轨道模型和双流体模型,探讨了气速、气体物性和固相颗粒浓度对FCC沉降器粗旋料腿泄气率的影响规律。结果表明,气速和固相颗粒浓度升高均导致粗旋料腿内外压差增大,料腿泄气率随之增大。随固相颗粒浓度增大,料腿泄气率上升的趋势先急后缓,与其固相颗粒浓度-压降关系相对应,料腿泄气率-固相颗粒浓度曲线和压降-固相颗粒浓度曲线显示的转折点质量浓度均为0.8 kg/m3;固相颗粒浓度对料腿泄气率的影响存在着2种作用机制,即下行颗粒群对气体的夹带作用和颗粒在粗旋内壁形成的不断增厚的灰层对气体实际流通横截面积的缩减作用。气体密度的增大会导致料腿泄气率增大;黏度增加在削弱气流的旋转能量的同时,增加了升气管短路流率,对料腿泄气率的增加具有正反两方面作用。综合操作参数、气体物性和结构尺寸等因素的影响,回归得到FCC沉降器粗旋料腿泄气率表达式。

催化裂化第三级旋风分离器的现状和发展方向

结合目前我国所采用的多管式三旋近几年运行过程中出现的问题和对烟气轮机正常运转的影响,重点分析了这些问题产生的原因,提出了采用国外常用的另一种旋风式三旋方案解决多管式三旋单管并联后返混严重,影响三旋总体效率和单管粉碎催化剂促使烟气轮机叶片结垢的问题。并介绍了旋风式三旋的主要结构和结构特点。

卧式三旋内多管间窜流返混的数值模拟

利用数值模拟的方法,采用Reynolds应力输运模型和随机轨道模型,对一种卧式第三级旋风分离器实验装置内的湍流气粒两相流动进行了全尺寸的数值模拟,主要考察了不同的泄气率、各旋风单管等压力降和不等压力降对装置集尘室内排尘口附近的流动状况的影响。结果表明,各旋风单管的工作状态并不相同,并导致窜流返混的发生,影响了三旋的分离效率;此外,计算结果还表明,适度提高泄气率有助于抑制三旋单管间的窜流返混,为三旋的优化设计提供了理论依据。

立式天然气多管旋风分离器内流体的流动特性

利用数值模拟的方法,采用Reynolds应力输运模型和随机轨道模型,对一种立式天然气多管旋风分离内的湍流气粒两相流动进行了全尺寸的数值模拟。为了反映真实的流动过程,计算过程中对进气室、集气室、集尘室及各轴流旋风分离器等复杂结构没有进行简化,并实现了完全结构化的网格划分。结果表明,除尘器内各旋风单管的工作状态并不相同,集尘室内含尘气体在各单管间发生窜流返混,影响了多管旋风分离的分离效率;此外,计算结果还表明,适度提高泄气率有助于抑制单管间的窜流返混,为天然气立式多管旋风分离的优化设计提供了理论依据。

摩托车铝合金轮圈的铸造模拟分析

利用计算机辅助分析软件,仿真铝合金轮圈铸造过程,以稳态收敛分析结果,观察冷却水、冷却气、模具初始温度、轮圈几何造型对轮圈铸造缩孔指标的影响。用仿真程序与缩孔、缩松预测轮圈铸造质量,找出最佳制程参数,从而降低轮圈压泄漏气率,提高轮圈铸造质量,降低生产成本。

低弗鲁德数条件下通气超空泡泄气机理数值模拟

基于RANS方程,采用分相流模型对超空泡在低弗鲁德数条件下的泄气机理进行了模拟,考虑了水-气两相之间的相互作用及重力效应。研究了不同湍流模型对泄气率的影响。得出了不同弗鲁德数和不同通气率条件下超空泡的泄气规律,与水洞试验现象一致。计算结果与经典经验公式对比表明数值方法具有很好的计算精度,对进一步研究通气超空泡的物理机制具有重要意义。

Numerical investigation of turbulent bubbly wakes created by the ventilated partial cavity

This paper presents a numerical study on the turbulent bubbly wakes created by the ventilated partial cavity.A semi-empirical approach is introduced to model the discrete interface of the ventilated cavity and its complex gas leakage rate induced by the local turbulent shear stress.Based on the Eulerian-Eulerian two-fluid modeling framework,a population balance approach based on MUltiple-SIze-Group (MUSIG) model is incorporated to simulate the size evolution of the sheared off microbubbles and its complex interactions with the two-phase flow structure in the wake region.Numerical predictions at various axial locations downstream of the test body were in satisfactory agreement with the experimental measurements.The captured bubbly wake structure illustrates that the bubbles may disperse as a twin-vortex tube driven by gravity effect.The predicted Sauter mean bubble diameter has confirmed the dominance of the coleascense process in the axial direction.As the bubbles develop downstream,the coleascense and breakup rate gradually reach balance,resulting in the stable bubble diameter.A close examination of the flow structures,gas void fraction distributions and the bubble size evolution provides valuable insights into the complex physical phenomenon induced by ventilated cavity.

Turbine Endwall Film Cooling With Combustor-Turbine Interface Gap Leak- age Flow: Effect of Incidence Angle

This paper is focused on the film cooling performance of combustor-turbine leakage flow at off-design condition. The influence of incidence angle on film cooling effectiveness on first-stage vane endwall with combustor-turbine interface slot is studied. A baseline slot configuration is tested in a low speed four-blade cascade comprising a large-scale model of the GE-E 3 Nozzle Guide Vane (NGV). The slot has a forward expansion angle of 30 deg. to the endwall surface. The Reynolds number based on the axial chord and inlet velocity of the free-stream flow is 3.5 × 10 5 and the testing is done in a four-blade cascade with low Mach number condition (0.1 at the inlet). The blowing ratio of the coolant through the interface gap varies from M = 0.1 to M = 0.3, while the blowing ratio varies from M = 0.7 to M = 1.3 for the endwall film cooling holes. The film-cooling effectiveness distributions are obtained using the pressure sensitive paint (PSP) technique. The results show that with an increasing blowing ratio the film-cooling effectiveness increases on the endwall. As the incidence angle varies from i = +10 deg. to i = 10 deg., at low blowing ratio, the averaged film-cooling effectiveness changes slightly near the leading edge suction side area. The case of i = +10 deg. has better film-cooling performance at the downstream part of this region where the axial chord is between 0.15 and 0.25. However, the disadvantage of positive incidence appears when the blowing ratio increases, especially at the upstream part of near suction side region where the axial chord is between 0 and 0.15. On the main passage endwall surface, as the incidence angle changes from i = +10 deg. to i = 10 deg., the averaged film-cooling effectiveness changes slightly and the negative incidence appears to be more effective for the downstream part film cooling of the endwall surface where the axial chord is between 0.6 and 0.8.