动态旋流器内油水两相分离数值模拟

采用雷诺应力模型和多相流模型中的混合物模型,对动态旋流器内油水两相分离进行数值模拟研究,得到了油水两相分离过程、油相体积分数分布以及两相速度分布等情况。并探讨了其内部油相体积分布、油相与水相速度分布等规律。     

油水两相流润滑轧机油膜轴承的摩擦行为分析

目的研究含水润滑油对轧机油膜轴承的摩擦学性能的影响。方法选取轧机油膜轴承为研究对象,利用油水两相流体数学模型和弹流润滑方程研究轧机油膜轴承在等温条件下的润滑特性,分析油水两相流体润滑膜的压力、膜厚分别随含水率、滑滚比、轴颈间隙、主轴转速和轧制力的变化关系。结果水介入润滑油之后,随着含水率的增加,油水两相流体的黏度先增加,在含水率为30%左右时达到最大值(0.08 Pa·s),之后又迅速减小,直至接近于纯水的黏度(0.001 Pa·s)。当含水率为30%时,无量纲膜厚达到最大值(0.82),当含水率为90%时,无量纲膜厚达到最小值(0.68)。结论随着含水率的增加,油水两相流体由油包水流型转化为水包油流型,压力变化不大,膜厚先增加后减小,作为润滑剂,油包水流型比水包油流型具有更好的润滑性能,且在流型转变点处的润滑性能最优。随着滑滚比和轧机油膜轴承主轴转速的增加,压力减小,承载能力减弱,膜厚增加,润滑性能增强。随着轴颈间隙和外部轧制力的增加,压力增加,承载能力增强,膜厚减小,润滑性能减弱。     

磨削液射流两相流流场特性的应用研究

应用两相流理论对磨削液射流冷却过程进行研究,将VOF方法引入磨削液流场的模拟仿真过程中,建立了磨削冷却射流的瞬态模型.利用有限体积法对两相流流场进行数值仿真,求出了在不同位置以不同速度向磨削引入区射流时,气液两相流流场的压力、速度及磨削液的体积分布特性.仿真结果与实验结果符合得很好.计算结果表明:两相流理论模型比单相流模型能更真实地模拟磨削冷却过程.通过分析仿真结果,提出了一种判断磨削过程中冷却液冷却效果好坏的方法.通过仿真给出了磨削液供给充足时出口边界的确切位置,并得出了磨削液是沿着砂轮边缘而不是沿着工件表面离开磨削区的结论.     

应用CFD-DEM耦合模拟计算排泥管及法兰连接处固液两相流

对于管内固液两相流数值模拟,一般的做法是将固体颗粒相视为拟流体,采用多相流的CFD方法计算,这难以体现固体颗粒形状大小、碰撞、凝聚和分离等特性.选取常规的两段管径为0.7 m水平排泥管道和一个连接法兰段作为研究对象,运用CFD软件ANSYS-FLUENT模块与离散元软件EDEM耦合求解排泥管内及法兰连接处固液两相流.计算的来流速度为5.0 m/s,固体颗粒密度为1 300 ~2 300 kg/m3,固体颗粒入口体积率为10%~30%,粒径在20~60 mm范围内随机变化.因加工和安装的问题导致在管道法兰连接处存在凸出或凹进不平顺的情况.计算得到了在不同的法兰连接状况下的固液两相流场、固体颗粒轨迹和固相体积率分布等结果.     

高炉冷却壁冷却水管内液固两相流强化传热实验研究

针对高炉冷却壁管内污垢沉积而导致传热效率低的问题,提出在高炉冷却壁管内加入固相颗粒以形成液固两相流,在防止污垢的沉积及清洗污垢的同时,增加流体的扰动强化管内对流传热.对液固两相流和单相流的传热性能进行了对比实验.结果表明,由于固相颗粒的扰动和剪切效应,不仅可以强化管内传热,而且也可以在线清洗管内污垢,在流速为2 m/s,固相体积分数为3.5%～5.0%、固相粒径为2～3 mm的范围内,与单相流相比,液固两相流的传热系数提高了20%～45%.实验结果为液固两相流的工业应用提供了基础.     

PdW20包晶合金的凝固组织及相选择

考察了凝固速率在50~1.8×103μm/s范围内的PdW20合金凝固组织及凝固速率对微观组织形态和领先相的影响。结果表明,三种不同凝固条件下的凝固组织由初生W相、包晶(Pd)相和固溶体Pd相组成。随着凝固速率增大,合金组织从树枝晶转变成等轴晶,晶粒大小快速减小。合金组织存在显微偏析,并且随着凝固速率增大,晶内与晶界上的成分差值减小。在3.2×102μm/s凝固速率下,观察到领先相W在进行包晶反应时不完全,还有部分W剩余。     

冷却速度对钒微合金钢的组织和析出相的影响

采用光学显微镜和透射电镜研究了不同冷却速度下钒微合金钢的微观组织和析出相变化规律。结果表明:当冷却速度小于或等于5℃/s时,钢的组织均为铁素体+珠光体,且随着冷却速度的增加,铁素体的晶粒尺寸明显变细。当冷却速度达到10℃/s时,钢的组织变为马氏体+少量铁素体。透射电镜研究显示:平衡态时析出相包含大量弥散分布的尺寸主要为45~100 nm的不规则形V(C,N)相和(V,Ti)(C,N)复合相,当冷却速度小于或等于5℃/s时,析出相数量无明显改变,但颗粒尺寸随冷却速度的增加不断减小;但当冷速达到10℃/s时,析出相的数量显著下降,尺寸变小。对含钒微合金钢而言,调整适当的冷却速度,不仅可以细化铁素体晶粒,还可以提高析出强化效果,从而提高钢材的强韧性。     

热轧高强钢MAT3830两相区变形后不同速度冷却后的组织

采用Servotest热模拟试验机,对热轧高强钢MAT3830进行了包括两相区(α+γ)变形、等温弛豫和冷却等系列模拟试验.利用光学显微镜、扫描电镜和EBSD分析研究了两相区变形后不同冷却速度对显微组织的影响.结果表明,在较低冷速(1℃/s)时,显微组织由铁素体和珠光体组成,加速冷却(15℃/s)的试样在应变奥氏体的变形带上形成了针状铁素体,淬水(70℃/s)试样铁素体含量并不增加,但亚结构的形貌与相邻的铁素体晶粒不同.     

弯管液固两相流冲蚀失效模拟分析

目的分析流体参数、砂粒参数、环境参数对液固两相流弯管冲蚀失效的影响。方法利用FLUENT模拟弯管冲刷腐蚀,分析流速、粒径、砂粒质量流量、操作压力、重力方向对弯管冲蚀的影响。结果管内流速从2 m/s增加到10 m/s,最大冲刷腐蚀速率从8.86×10-8 kg/(m2·s)增加到2.45×10-7kg/(m2·s);颗粒粒径从75μm增加到200μm,再增加到550μm,最大冲蚀速率先从2.04×10-7 kg/(m2·s)减小至1.5×10-7 kg/(m2·s),后增加到2.66×10-7 kg/(m2·s);砂粒流量从0.05 kg/s增加到0.25 kg/s,最大冲蚀速率从8.56×10-8 kg/(m2·s)增加到3.20×10-7 kg/(m2·s);管内操作压力从0.1 MPa增加到0.9 MPa,最大冲蚀速率从1.50×10-7 kg/(m2·s)减少至1.25×10-7 kg/(m2·s);弯头出口由垂直向下位置变化为垂直向上,冲刷腐蚀速率从1.50×10-7 kg/(m2·s)逐渐增加至1.86×10-7 kg/(m2·s)。结论流速与冲刷腐蚀呈正相关关系;随着砂粒直径的增加,最大冲刷腐蚀速率先减小后增加;在一定范围内,最大冲刷腐蚀速率随着砂粒流量增加而增加;管内操作压力的变化对冲蚀减弱现象影响不明显;出口垂直向上时,冲蚀破坏最严重。     

RH真空精炼系统气液两相循环流动的均相流模型

提出一种修正的均相流模型，即在模型的含气率守恒方程中引入气相水平滑移速度，该速度只存在于喷嘴附近的区域，其物理作用是将气体导入流体中．计算实践表明，修正的均相流模型能够解决侧吹装置中的气液两相流动问题．同水模型的实验观察比较表明，该模型模拟的气相分布特征同水模型观察结果符合较好．     

Direct evidence for competition between metastable ω and equilibrium α phases in aged β-type Ti alloys

Precipitation response of a recently developed b-type Ti–25Nb–2Mo–4Sn alloy(wt%) during aging was investigated in detail. Experimental results indicate that the metastable ω or equilibrium α phase can form alternatively even under the same aging condition, depending on the condition prior to the aging, i.e., solution treatment or severe cold rolling. This provides, for the first time, the direct evidence for the competition between ω and α in aged β-type Ti alloys. This peculiar aging response is found to be closely related to high-density dislocations and grain boundaries which suppress the formation of ω but favor the precipitation of fine a phase.     

国外钢结硬质合金新进展

文中概括地论述了近年来国外钢结硬质含金发展的特点，指出钢结硬质合金硬质相正在向多样化方向发展，作为粘结相的钢种不断扩大，相成分范围明显拓宽．其生产手段进一步扩大和应用范围日益广泛，并列举了一些新型钢结硬质合金的实例．     

The Ag–Cu–Ge ternary phase diagram

The Ag–Cu–Ge phase diagram is not very well elaborated. In this work an attempt is made to validate the phase diagram in the area of the ternary eutectic and to decide whether it is a suitable model system for solidification experiments. The different steps in the solidification sequence are separately discussed and analysed. It is shown that an optimization of the system is necessary. The experiments in this work demonstrate that the transition reaction Ge is located closer to the ternary eutectic than assumed in earlier work.     

D-KH法制备金锡合金的组织与结构

通过D-KH法和熔铸法、急冷法制备的AuSn20合金相组成和相结构比较，表明了采用D—KH法制备的不同厚度AuSn20箔带和用3种方法制造的Ausn20合金的相组成和相结构完全相同。     

应力对核反应堆压力容器大型锻件用钢相变动力学和相变塑性影响的研究

以核反应堆压力容器 (RPV)大型锻件常用钢为对象 ,研究了应力对贝氏体相变的相变动力学及相变塑性的影响 ,得到定量描述应力诱导相变及相变塑性的模型 ,为下一步利用数值模拟优化该钢的热处理工艺打下了基础     

Experimental study of the isothermal section of the Ho-Fe-Cr system at 873 K

The isothermal section of the Ho-Fe-Cr ternary system was investigated by means of X-ray powder diffraction (XRD), metallography and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The ternary compound HoFe_12−xCr_x (x = 2) was characterized and the homogeneity range of the various ternary solutions was studied. It crystallizes with ThMn₁₂-type structure, space group I4/mmm and unit parameters a = 0.8406 nm and c = 0.4756 nm. The homogeneity range in HoFe_12−xCr_x was determined as x = 1.9-3.6, i.e. 14.6-27.7 at.% Cr. The maximum solid solubilities of Cr in Fe, Ho₂Fe₁₇, Ho₆Fe₂₃, HoFe₃ and HoFe₂ are about 28.0 at.%, 4.0 at.%, 13.0 at. %, 3.0 at.% and 11.0 at.%, respectively.     

A theoretical study of the phase equilibria in the Cu---Cr---Zr system

Small additions of chromium to Cu---Zr alloys or zirconium to Cu---Cr alloys are widely used to improve the mechanical properties of the alloys at high temperatures. There are conflicting opinions in the literature on the question of the existence of the pseudobinary system Cu---Cr₂Zr. From calculation of the Cu---Cr---Zr phase diagram using the CALPHAD method, the possibility of the existence of this pseudobinary has been ruled out. A number of isothermal and vertical sections have been calculated together with the liquidus surface. The reaction scheme for the whole system is also presented.     

The isothermal section of Dy-Co-Cr ternary system at 500 °C

The isothermal section of the Dy-Co-Cr ternary system at 500 °C was investigated by X-ray powder diffraction (XRD), metallography and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The isothermal section consists of 11 single-phase regions, 20 two-phase regions and 10 three-phase regions. The only ternary compound DyCo_12−xCr_x (space group I4/mmm) with ThMn₁₂-type structure was confirmed in this system. The homogeneity range in DyCO_12−xCr_x was found to be about x = 3.6-4.4. The lattice parameters for DyCO_12−xCr_x with 3.6 ≤ x ≤ 4.4 are a = 0.8312-0.8334 nm and c = 0.4706-0.4722 nm. The maximum solid solubilities of Cr in Dy₂Co₁₇, DyCo₃ and DyCo₂ are about 16.0, 5.0 and 17.0 at.%, respectively.     

An investigation of the Al-Rh-Ru phase diagram above 50 at.% Al

Partial 1100, 1000, 900 and 700 °C isothermal sections of the Al-Rh-Ru phase diagram were determined. The isostructural binary AlRu and AlRh phases probably form a continuous β-range of the CsCl-type solid solutions. The Al₉Rh₂ and C-Al₅Rh₂ dissolve up to 4.5 and 13 at.% Ru, while Al₁₃Ru₄ and Al₂Ru dissolve up to 14.5 and 8 at.% Rh, respectively. A ternary orthorhombic structure (Pbma, a = 2.34, b = 1.62 and c = 2.00 nm) related to the Al-Rh ?-phases was revealed at the extension of the Al-Rh ?-phase area at compositions up to Al₇₇Rh₁₅Ru₈.