AP1000次级汽水分离器分离性能及结构优化的数值研究

建立AP1000次级波纹板汽水分离器内两相流动的数学模型,随后数值模拟波纹板内的两相流动,并分析其分离性能。进而对波纹板结构进行优化,得到具有较高分离效率和较低流动阻力的新型波纹板。首先分别建立波纹板内部蒸汽相和液滴相运动的数学模型。然后通过自编程序与Fluent软件耦合对该两相流动模型数值求解。随后得到波纹板进出口总压降,并通过模拟液滴在波纹板内的运动轨迹,得到波纹板的分离效率和内部液滴湿度分布。进而以分离效率和流动压降为目标优化波纹板结构,设计得到具有较高分离效率和较低流动阻力的新型波纹板。本文提出的数值模拟方法对汽水分离器结构的设计和优化具有较强的指导意义。     

Particulate flow modelling in a spiral separator by using the Eulerian multi-fluid VOF approach

The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator,and thus a Eulerian multi-fluid volume of fluid(VOF) model was first proposed to describe the particulate flow in spiral separators. In order to improve the applicability of the model in the high solid concentration system, the Bagnold effect was incorporated into the modelling framework. The capability of the proposed model in terms of predicting the flow film shape in a LD9 spiral separat...     

半逆流型磁选机在梅山选矿厂的应用

2004年梅山选矿厂在降磷弱磁作业7#系列采用半逆流型磁选机代替顺流型磁选机,试验表明,其精矿品位、金属回收率均高于6#系列,尾矿品位低于6#系列.本文分析了两种磁选机的工作原理,指出了应用中存在的问题,并提出了解决方法.     

裂解气压缩机EC-1301干气密封国产化改造与应用

介绍了干气密封的工作原理,通过对现场条件的论证,选用串联式干气密封;阐述了干气密封结构的设计;成功地完成EC-1301的干气密封国产化改造;填补了国内该项技术的空白,标志着我国干气密封设计制造技术达到了国际先进水平,有推广价值.     

Dynamic Changes in Reactive Oxygen Species in the Shoot Apex Contribute to Stem Cell Death in Arabidopsis thaliana

In monocarpic plants, stem cells are fated to die. However, the potential mechanism of stem cell death has remained elusive. Here, we reveal that the levels of two forms of reactive oxygen species (ROS), superoxide anion free radical (O2·−) and hydrogen peroxide (H₂O₂), show dynamic changes in the shoot apex during the plant life cycle of Arabidopsis thaliana. We found that the level of O2·− decreased and disappeared at four weeks after bolting (WAB), while H₂O₂ appeared at 3 WAB and showed a burst at 5 WAB. The timing of dynamic changes in O2·− and H₂O₂ was delayed for approximately three weeks in clv3-2, which has a longer lifespan. Moreover, exogenous application of H₂O₂ inhibited the expression of the stem cell determinant WUSCHEL (WUS) and promoted the expression of the developmentally programmed cell death (dPCD) marker gene ORESARA 1 (ORE1). These results indicate that H₂O₂ triggers an important signal inducing dPCD in stem cells. Given that O2·− plays roles in maintaining WUS expression and stem cell activity, we speculate that the dynamic shift from O2·− to H₂O₂ in the shoot apex results in stem cell death. Our findings provide novel insights for understanding ROS-mediated regulation during plant stem cell death.     

尿素生产旋风分离器腐蚀与对策

论述了尿素生产旋风分离器的结构、工作工艺条件;重点分析了分离器发生腐蚀的原因;针对不同的腐蚀原因提出了具体的优化措施,收到了良好的技改效果。     

多翼离心风机主要部件对风机流动特性影响的研究现状

叶轮内流场是影响风机气动及噪声性能最重要的因素,因而对其进行深入研究具有重要意义。本文根据多翼离心风机主要部件的结构特点,回顾了近年来国内外有关风机流动特性的研究现状。得出影响多翼离心风机性能的主要因素有：气流分布不均匀,蜗舌附近的旋涡,气流的分离及回流,风机前后盘的二次涡区域。今后研究的一个主要方向应是在试验研究的同时,采用CFD手段研究多翼离心风机内流场特征,并在风机设计时反映上述影响因素,从而有效地降低风机噪声、提高风机效率。     

卧螺离心机结构的研究及发展

卧螺离心机是应用范围较广的一种离心机,它在离心机领域中一直占有重要地位。在介绍卧螺离心机结构的基础上,综述了卧螺离心机结构形式的改进,总结了有限元法在卧螺离心机转鼓和螺旋输送器强度分析上的应用,并对卧螺离心机存在的问题及发展方向进行了讨论。     

Optimal design of drainage channel geometry parameters in vane demister liquid–gas separators

Vane liquid–gas demisters are widely used as one of the most efficient separators. To achieve higher liquid disposal and to avoid flooding, vanes are enhanced with drainage channels. In this research, the effects of drainage channel geometry parameters on the droplet removal efficiency have been investigated applying CFD techniques. The observed parameters are channel angle, channel height and channel length. The gas phase flow field was determined by the Eulerian method and the droplet flow field and trajectories were computed applying the Lagrangian method. The turbulent dispersion of the droplets was modeled using the discrete random walk (DRW) approach. The CFD simulation results indicate that by applying DRW model, the droplet separation efficiency predictions for small droplets are closer to the corresponding experimental data. The CFD simulation results showed that in the vane, enhanced with drainage channels, fewer low velocity sectors were observed in the gas flow field due to more turbulence. Consequently, the droplets had a higher chance of hitting the vane walls leading to higher separation efficiency. On the other hand, the parameters affect the liquid droplet trajectory leading to the changes in separation efficiency and hydrodynamic characteristic of the vane. To attain the overall optimum geometry of the drainage channel, all three geometry parameters were simultaneously studied employing 27 CFD simulation cases. To interpolate the overall optimal geometry a surface methodology method was used to fit the achieved CFD simulation data and finally a polynomial equation was proposed.     

Unsteady pressure measurements in a high-speed centrifugal compressor

This paper presents the unsteady data acquisition system used to measure the pressure field in high speed compressors. Details and electronic sketches are given for the conditioners developed in-house that have been used to amplify and to filter the pressure signal with the aim of acquiring data up to 150 kHz. A discussion of the experimental results carried out in a centrifugal compressor is proposed. Through different processing of the pressure signals and a comparison with URANS simulations, the excitation of the pressure transducers by the pressure waves generated by shock waves that occur between the impeller and the diffuser is highlighted. The levels of pressure fluctuations measured when entering into surge are also presented and reveal very repetitive behaviour of the flow instabilities.