Application of Fractal Contact Model in Dynamic Performance Analysis of Gas Face Seals

Fractal theory provides scale?independent asperity contact loads and assumes variable curvature radii in the contact analyses of rough surfaces, the current research for which mainly focuses on the mechanism study. The present study introduces the fractal theory into the dynamic research of gas face seals under face?contacting conditions. Structure?Function method is adopted to handle the surface profiles of typical carbon?graphite rings, proving the fractal con?tact model can be used in the field of gas face seals. Using a numerical model established for the dynamic analyses of a spiral groove gas face seal with a flexibly mounted stator, a comparison of dynamic performance between the Majumdar?Bhushan(MB) fractal model and the Chang?Etsion?Bogy(CEB) statistical model is performed. The result shows that the two approaches induce differences in terms of the occurrence and the level of face contact. Although the approach distinctions in film thickness and leakage rate can be tiny, the distinctions in contact mechanism and end face damage are obvious. An investigation of fractal parameters D and G shows that a proper D(nearly 1.5) and a small G are helpful in raising the proportion of elastic deformation to weaken the adhesive wear in the sealing dynamic performance. The proposed research provides a fractal approach to design gas face seals.     

高效液相色谱氢化物发生原子荧光光谱联用检测海藻中砷形态

目的测定14种海藻样品中总砷和无机砷的含量,同时分析样品中6种砷形态。方法将海藻样品经过微波消解的前处理方法,通过电感耦合等离子体质谱(inductively coupled plasma mass spectrometry,ICP-MS)测定总砷含量;根据国标方法中无机砷检测的前处理方法,通过原子荧光光谱(atomic fluorescence spectrometry,AFS)测定无机砷含量;最后通过酸提的前处理方法,利用高效液相色谱-氢化物发生-原子荧光光谱法(high performance liquid chromatography-ultraviolet photo-oxidation-hydride generation-atomic fluorescence spectrometry,HPLC-(UV)-HG-AFS)测定海藻样品中6种形态砷含量并与国标无机砷方法比较。结果 14种海藻样品中总砷含量为0.038~46.2 mg/kg;无机砷含量为0.006~19.3 mg/kg;对HPLC-(UV)-HG-AFS仪器的优化和方法的摸索后,从海藻样品中主要测得的砷形态为As(III)、As(V)和DMA,MMA含量较少,没有测出As B和As C。结论在砷形态较为复杂的海藻样品检测中,通过HPLC-(UV)-HG-AFS检测方法可以有效避免无机砷前处理中可能出现的有机砷向无机砷转变的现象,降低干扰,增加测试的准确性,更为具体地表现海藻样品中主要的砷形态含量。     

Prediction of droplet size distribution in sprays of prefilming air-blast atomizers

Droplet size distribution is a crucial parameter of atomization process besides droplet mean diameter. In this paper, the finite stochastic breakup model (FSBM) of prefilming air-blast atomization process has been proposed according to the self-similarity of droplet breakup. There are four parameters in FSBM, which are the initial droplet diameter D₀, the maximum stable droplet size D_c, the minimum mass ratio of a sub-droplet to the mother droplet a, and the droplet breakup probability P(D). The simulation results of droplet size distribution with this model agreed well with the experimental results of prefilming air-blast atomizers. With this model, the nonlinear relationship between the mean droplet diameters and droplet size distribution of the air-blast atomization process can be predicted exactly.     

利用系统摄动建立施工工序的连接系数

利用系统的摄动原理建立了工序间的连接系数、断接系数概念及计算公式 ,并提出了工序特征指标的摄余量、摄近量     

Synthesis, crystal structure and X-ray excited luminescent properties of LuBa3B9O18

A new compound LuBa₃B₉O₁₈ has been prepared by a high-temperature solid-state reaction and its crystal structure was determined by powder X-ray diffraction methods. The results of Rietveld refinement show that it is isotypic to YBa₃B₉O₁₈. The X-ray excited luminescent properties of LuBa₃B₉O₁₈ were investigated. It shows a broad emission band in the wavelength range of 300–550 nm with peak center at 385 nm. Its room temperature fluorescent decay profile exhibits a single-exponent shape with decay time of 15 ns. It is believed that the lattice defects have played an important role on the luminescent performances of LuBa₃B₉O₁₈ powders and its thermal luminescence measurement confirmed the existence of lattice defects in it. Considering the emission wavelength, luminescence intensity, decay time, melting point, density and non-hygroscopic property of LuBa₃B₉O₁₈, one has reason to assume that it might find an application as a new scintillation material.     

Preparation of CuInSe2 thin films by selenization of co-sputtered Cu-In precursors using rapid thermal processing

CuInSe₂ thin films have been synthesized by selenization of co-sputtered Cu-In precursors using rapid thermal processing (RTP). Heat treatments from 400 to 450 °C for periods between 1 min and 10 min were carried out on (Cu-In)/Se precursors. Phase evolution as function of reaction temperature and holding time was analyzed according to XRD and SEM results. Severe Se loss during RTP was proved in our experiments and has been reported by many other researchers. To solve the problem, a new effective way of reducing Se loss was presented, which is based on low temperature heat treatment at 250 °C before high temperature annealing. Nearly single-phase CuInSe₂ thin films have been achieved by annealing precursors at 250 °C for 5 min then 450 °C for 1 min. Se loss can be significantly reduced via low temperature heat treatment by the fact that under 250 °C, Se is evaporated mildly and largely consumed as Cu-Se and In-Se binary selenides.     

Three-dimensional CFD simulations to study the effect of impeller geometry on internal flow field in ADS upward spiral flow target

The relationship between flow field characteristics and geometrical structures is an important issue in designing liquid metal spallation target for accelerator-driven sub-critical system (ADS). Upward spiral flow target (USFT) is a new type ADS windowless target in which an impeller is employed to generate upward spiral flow and regulate internal flow field. The impeller comprises a central shaft and several identical blades, and its geometry is very crucial for designing the target. In this paper, series models with different geometric parameters of the shaft and the blades are simulated by ANSYS CFX to analyse the distributions of internal flow field and the dimensions of stagnation zone in USFT. The results show that the shaft plays a primary role in guiding the upward flow while the blades are significant for generating the spiral flow. Finally, an optimized model with preferred geometric parameters is obtained by comparing the overall simulation results. The whole research has foundational signification for further studying USFT.     

特大型隔爆外壳户外防爆试验方法研究

介绍了特大型隔爆外壳试验的防爆试验方法、试验准备、外壳耐压及内部点燃不传爆试验项目。     

Optimal quantization method for uneven-phase diffractive optical elements by use of a modified iterative Fourier-transform algorithm

A method based on an iterative Fourier-transform algorithm (IFTA) with phase optimization for phase-only multilevel diffractive optical elements (DOEs) is presented. Phase optimization by minimizing the mean-squared error composed of an amplitude-weighted probability-density function is performed in the IFTA iterations to ensure that the wavefront difference is minimized and thus to improve the DOEs' performance. Using the proposed method, we obtained a small standard deviation of diffraction efficiency of 20 uneven-phase DOEs, showing that DOEs with high diffraction efficiency did not vary significantly with the initial conditions. The simulation results of even- and uneven-phase four-level DOEs designed by use of direct and stepwise quantization IFTA methods are compared.