小型轴流CPU风扇设计与数值模拟

根据空气强迫对流冷却系统一体化设计理念,对小型轴流CPU风扇进行空气动力设计,由Fortran输出三维空间曲线文件,导入Pro/E实现实体造型.通过标准风洞对CNC铣床雕刻出的样品进行风扇性能测试.为了减少费用和缩短设计周期,利用CFD对风扇性能预测,风扇出口流向角结论为曲线型散热器设计提供依据;数值模拟结果与实验特性曲线比较吻合,为一体化数值模拟积累了经验.     

过滤风速对纤维过滤器压力损失的试验研究

从理论上分析了过滤风速对纤维压力损失的影响,用ORIGIN软件给出数学模拟曲线。介绍了试验设备及测试方法,通过试验得出过滤风速和压力损失变化关系。     

Aggregation behavior of block polyethers with branched structure at air/water surface

The block polyethers with various branch structure, such as TEPA[(PO)₃₆(EO)₁₀₀]₇, TEPA[(PO)₃₆(EO)₁₀₀(PO)₃₆]₇, and TEPA[(PO)₃₆(EO)₁₀₀(PO)₅₆]₇ were synthesized. Moreover, the aggregation behavior was investigated via the measurements of equilibrium surface tension, dynamic surface tension, and surface dilational viscoelasticity, in order to probe the effect of the block structure on the property of the branched block polyethers. The surface tension results show that the efficiency and effectiveness of the block polyethers to lower surface tension increase with the increase of the PO group numbers. The maximum surface excess concentration (Γ_max) values and the minimum occupied area per molecule at the air/water interface (A_min) values of the branched block polyethers obtained from Gibbs adsorption equations increase and decrease with the increases of the PO group numbers, respectively. The dynamic parameters n and t^* representing the diffusion speed of the polyether molecules from bulky solution to the subsurface and from the subsurface to the air/water surface are obtained according to the equation proposed by Rosen. The results show that the n values firstly increase and then decrease and t^* values decrease with the increase of the polyether concentrations. The results of surface dilational viscoelasticity show that the dilational modulus of TEPA[(PO)₃₆(EO)₁₀₀(PO)₅₆]₇ is the largest among the three block copolymers at the low concentration (<1 mg L⁻¹) but that of TEPA[(PO)₃₆(EO)₁₀₀]₇ is the largest at the high concentration (>1 mg L⁻¹).     

Identification of mononitropyrenes and mononitrofluoranthenes in air particulate matter via fused silica gas,chromatography combined with negative ion atmospheric pressure ionization mass spectrometry

This paper describes the use of high resolution capillary gas chromatography combined with negative ion atmospheric pressure ionization mass spectrometry (NIAPIMS) for the analysis of an air particulate extract for mononitropyrenes and mononitrofluoranthenes, some of which are powerful bacterial mutagens. The results are compared to those obtained by the electron impact mass spectrometric analysis of the same sample In addition, the NIAPIMS method confirmed the identification of 4-nitropyrene in the ambient air sample.     

Determination of slug permeability factor for pressure drop prediction of slug flow pneumatic conveying

Current models for pressure drop prediction of slug flow pneumatic conveying in a horizontal pipeline system assume some type of steady state conditions for prediction,which limits their capability for increased predictive accuracy relative to experimental data.This is partly because of the nature of slug flow pneumatic conveying system,which,as a dynamic system,never becomes stable.By utilising conservation of mass (airflow),a dynamic pressure analysis model is proposed on the basis of the derivative of the upstream pressure behaviour.The rate of air permeation through slug,one of the important factors in the conservation model,is expressed as a function of a slug permeability factor.Other factors such as slug velocity,slug length and the fraction of stationary layer were also considered.Several test materials were conveyed in single-slug tests to verify the proposed pressure drop model,showing good agreement between the model and experimental results.     

喷水室典型空气处理过程中空气流速的实验研究

针对纺织厂空调系统的核心-喷水室,研究喷水室内处理空气的冷却减湿和等焓加湿两个典型热湿交换过程。提出Re准数对传热传质有显著作用,而Re数的大小取决于流体速度。通过实验研究当空气流速从3m/s提高到5m/s时对喷水室热湿交换性能的影响,从而确定空气流动速度因素对两个热湿交换效率的影响趋势。根据拟合的数学曲线,总结出当空气的流动速度提高后,热湿交换效率相应提高。从而推动高速喷水室在实际工程中的应用。     

The effect of air exposure on palladium–copper composite membranes

It was found that when electrolessly deposited thin Pd and Pd–Cu membranes were exposed to air at temperatures above 350 °C, their H₂ flux increased substantially immediately after the air exposure, then decreased to a new steady-state value. While this was a quasi-reversible change for the H₂ flux, the flux of insoluble species, such as N₂, irreversibly increased with every air exposure but by a much smaller extent. The extent of these changes was found to be dependent on the exposure time and the temperature of the tests. Thus, we decided to investigate the effect of gas exposures on the properties of these materials.

Palladium and palladium–copper films, prepared by electroless deposition on ceramic supports, and commercial foils were exposed to air, hydrogen and helium at 500 and 900 °C for times varying from 1 h to 1 week with the objective of determining the effect of the different exposure conditions on the surface morphology, the flux of different penetrants and the crystalline structure of the materials. Atomic force microscopy (AFM) and X-ray diffraction (XRD) were used to study the changes occurring in the films under those conditions.

It was observed that the exposure of both the electroless films and the foils to hydrogen and air markedly modified their surface morphology. The hydrogen exposure tended to smooth the surface features whereas the oxygen exposure created new surface features such holes and large peaks. Additionally it was found that the air exposure produced some oxidation of the film to create PdO.

These results suggested that a common hypothesis stating that air oxidation just cleans the surface of the membrane might not be sufficient to explain all of those changes. A contributing effect of air exposure may be the increase in surface area due to the formation of palladium oxide. However, the extent of the surface area increase was insufficient to explain the increase in steady-state H₂ flux.     

On the Quasi-regularity of Semi-Dirichlet Forms

We prove that if a right Markov process is associated with a semi-Dirichlet form, then the form is necessarily quasi-regular. As applications, we develop the theory of Revuz measures in the semi-Dirichlet context and we show that quasi-regularity is invariant with respect to time change.     

压缩空气蓄能(CAES)系统集成及性能计算

压缩空气蓄能(CAES)系统是一种新型电能存储系统,具有动态响应快、经济性能高、环境污染小等优点,可起到负荷平衡、战略规划、提高供电质量的作用。CAES系统包括空气压缩机、电动机/发电机、地下贮气室、换热器、燃烧室、燃气轮机等常用设备,可分为两个子系统,分别是蓄能子系统和发电子系统,通过对设备采取不同组态,可得到不同方案系统。本文将结合当前CAES发展的新技术,提出CAES系统的集成方案并进行相应的计算与优化。     

Effects of gas sparging and mechanical mixing on sonochemical oxidation activity

The effects of air sparging (0–16 L min⁻¹) and mechanical mixing (0–400 rpm) on enhancing the sonochemical degradation of rhodamine B (RhB) was investigated using a 28 kHz sonoreactor. The degradation of RhB followed pseudo first-order kinetics, where sparging or mixing induced a large sonochemical enhancement. The kinetic constant varied in three stages (gradually increased → increased exponentially → decreased slightly) as the rate of sparging or mixing increased, where the stages were similar for both processes. The highest sonochemical activity was obtained with sparging at 8 L min⁻¹ or mixing at 200 rpm, where the standing wave field was significantly deformed by sparging and mixing, respectively. The cavitational oxidation activity was concentrated at the bottom of the sonicator when higher sparging or mixing rates were employed. Therefore, the large enhancement in the sonochemical oxidation was attributed mainly to the direct disturbance of the ultrasound transmission and the resulting change in the cavitation-active zone in this study. The effect of the position of air sparging and mixing was investigated. The indirect inhibition of the ultrasound transmission resulted in less enhancement of the sonochemical activity. Moreover, the effect of various sparging gases including air, N₂, O₂, Ar, CO₂, and an Ar/O₂ (8:2) mixture was compared, where all gases except CO₂ induced an enhancement in the sonochemical activity, irrespective of the concentration of dissolved oxygen. The highest activity was obtained with the Ar/O₂ (8:2) mixture. Therefore, it was revealed that the sonochemical oxidation activity could be further enhanced by applying gas sparging using the optimal gas.