CFD在双吸式离心泵优化设计中的应用

针对某双吸式离心泵流量和扬程达不到设计要求,效率偏低的情况,对该泵内部三维湍流进行了数值模拟,通过对泵内流场和总压变化过程的分析,找出了该泵达不到设计要求的原因,提出了切割叶轮进口以扩大进口面积的改进方案.对改进后的泵内部流场进行了数值模拟,并与改进前泵内流场数值计算结果进行对比,性能预测表明改进后的泵基本达到了设计要求.在此基础上,对改进后的泵进行了实验测试,结果表明上述改进措施是有效的,数值模拟方法为水泵的优化设计提供了有力工具.     

带有涡流发生器的离心压气机内流动分析

本文采用数值计算方法对带有和不带有涡流发生器(Vortex Generator Jet,VGJ)的低速离心压气机叶轮内流动进行了数值模拟,分析了涡流发生器不同配置参数对压气机叶轮性能的影响,较为详细地揭示了叶轮内流动特性,数值计算结果证明了采用涡流发生器实现离心压气机叶轮内部流动控制的有效性.     

Numerical Assessment of the Hydrodynamic Behavior of a Volute Centrifugal Pump Handling Emulsion

Although emulsion pumping is a subject of growing interest, a detailed analysis of the fluid dynamic phenomena occurring inside these machines is still lacking. Several computational investigations have been conducted to study centrifugal pumps carrying emulsion by analyzing their overall performance, but no studies involved the rheological behavior of such fluids. The purpose of this study is to perform a computational analysis of the performance and flow characteristics of a centrifugal pump with volute handling emulsions and oil–water mixtures at different water cuts modeled as a shear-thinning non-Newtonian fluid. The studied pump consists of a five-bladed backward curved impeller and a volute and has a specific speed of 32 (metric units). The rheological properties of the mixtures studied were measured experimentally under a shear rate ranging from 1 s⁻¹ to 3000 s⁻¹ and were fitted to conventional Cross and Carreau effective viscosity models. Numerical results showed the flow topology in the pump is directly related to the viscosity plateau of the pseudoplastic behavior of emulsions. The viscosity plateau governs pump performance by influencing the loss mechanisms that occur within the pump. The larger the ν_∞, the less recirculation loss the fluid experiences, and conversely, the smaller the value of ν₀, the less friction loss the fluid experiences.     

离心压气机内激波/叶排相互作用

对根部存在疲劳裂纹的某跨音离心级进行了非定常流场数值研究,其中着重关注运动激波／叶排相互作用物理图画及其影响。研究表明:离心压气机中运动激波／叶排相互作用仍然服从一般激波／固壁相交行为规则;叶轮／扩压器间距小以及叶轮尾迹相对较宽造成扩压器内激波剧烈变化;扩压器前伸波深入叶轮通道深度由激波强度及扩压器前缘附近叶表形状决定;扩压器前伸波与叶轮尾缘相互作用可能是本叶轮根部尾缘发生高周疲劳的原因。     

Innovative Purification Method of Ovatodiolide from Anisomeles indica to Induce Apoptosis in Human Gastric Cancer Cells

Ovatodiolide (Ova), found in the plant Anisomeles indica (AI), has been reported to have an anti-proliferation effect in various cancer cells. However, little information is available regarding the anti-cancer effect of Ova in human gastric cancer cells. In this study, we investigated the inhibitory effects and the mechanisms of action responsible for these effects on human AGS cell lines from a newly developed purification technique for Ova from AI extract. Extract obtained at the optimum condition of 95% ethanol extraction of AI was sequentially partitioned by using different polarity solvents. Enriched content of Ova (35.9% purity) from the n-hexane fraction was then applied to the purification by using centrifugal partition chromatography (CPC) in a two-phase solvent system consisting of n-hexane:ethyl acetate:methanol:water (1.0:1.0:1.0:1.0, v/v/v/v) to reach purity over >95.0%. In evaluation of the anti-proliferation effect on AGS cells, Ova induced cell apoptosis with IC₅₀ values of 13.02 and 6.18 μM at 24 and 48 h, respectively, and arrested the cells at the G2/M phase. Quantification of Bax/Bcl2 mRNA expressions using qPCR showed a 2.5-fold increase in the Ova (5 μM)-treated cells at 48 h than in the control group. Specific protein expression data warrant further research to further confirm the proposed Ova-induced apoptotic pathway in AGS cells.     

N–Term Approximation in Anisotropic Function Spaces

In L₂(0, 1)²) infinitely many different biorthogonal wavelet bases may be introduced by taking tensor products of one–dimensional biorthogonal wavelet bases on the interval (0, 1). Most well–known are the standard tensor product bases and the hyperbolic bases. In [23, 24] further biorthogonal wavelet bases are introduced, which provide wavelet characterizations for functions in anisotropic Besov spaces. Here we address the following question: Which of those biorthogonal tensor product wavelet bases is the most appropriate one for approximating nonlinearly functions from anisotropic Besov spaces? It turns out, that the hyperbolic bases lead to nonlinear algorithms which converge as fast as the corresponding schemes with respect to specific anisotropy adapted bases.     

“首项分裂”的进一步验证及所发现的异常峰形

采用ＨＰ－５８９０Ａ气相色谱仪,ＨＰ－３３９２Ａ积分仪（工作在ＰＬＯＴ方式）,配用长３０ｃｍ、内径０．５ｍｍ涂ＤＮＰ的铜毛细管柱,柱温１００℃,０．１μＬ正十四烷为样品,采用单池热导及氢焰检测器,通过改变流速再次验证了“首项分裂”现象。完成实验的关键是设法克服伴随进样过程产生的干扰。实验过程中再次发现了异常峰形。     

Some Properties of Free Boundary for Solution of Porous Medium Equation with Gravity Term in One-dimension

Consider the degenerate parabolic equation (porous medium equation with gravity term): u_t = (u^m)_{xx} + (u^n)_x, -∞ < x < ∞, t > 0, m > 1 u(x, 0) = u_0(x), -∞ < x < ∞ The main results consist of the estimation of t^∗_i called waiting time, the behavior of pressure V = \frac{m}{m-1}u^{m-1} near a vertical or a nonvertical part of ς_i(t) and a condition of that ς_i(t) is continuously differentiable.     

一类带阻尼项非线性分数阶微分方程的振动性

研究一类带阻尼项非线性分数阶微分方程的振动性,利用Riccati变换和不等式技巧,得到了方程振动性的2个判定准则,并用例子验证了相关结果。