旋流数对旋流煤粉燃烧器NOx生成影响的研究

用数值模拟方法研究了旋流数改变对旋流燃烧器煤燃烧N0x生成的影响，给出了热N0x和燃料N0x生成的详细信息。预报结果表明，当二次风旋流数从0．204增加到0．414时，可以降低燃烧器出口区域燃料N0x的生成，同时可以保持煤粉颗粒较高的燃尽率，另外，模拟结果也表明，燃烧器出口区域的N0x生成主要是由燃料N0x的生成机理来控制，因此，适当提高旋流燃烧器的旋流数可以提高燃烧效率，降低N0x的生成。     

烟气脱硫反应中产物层形成过程特性分析

主要分析了脱硫反应产物层形成过程中的传递反应过程特性。研究发现，脱硫剂颗粒产物层形成过程与蒂勒数密切相关，至产物层形成时转化率仅仅决定于蒂勒数，随蒂勒数的增加而降低，与此阶段持续的时间无关，蒂勒数是描述脱硫反应产物层形成过程中传递反应特性的重要参数，它同时反映了化学反应速度、扩散速度的影响。本文还考察了粒径、孔隙分布方式以及温度对反应过程的影响，证实了随着温度和孔隙率的升高反应转化率相应提高，反应平均孔径在100～300nm之间的孔隙更利于进行脱硫反应，热重分析(TGA)实验结果进一步证实了理论分析的正确性。     

基于集对分析模型的巢湖流域水资源系统脆弱性评价

鉴于水资源系统脆弱性是一个复杂的系统工程,从水资源脆弱性、生态环境脆弱性和承载能力脆弱性三方面构建了流域水资源系统脆弱性指标体系,利用同异反层次法联系数建立了流域水资源系统脆弱性评价的集对分析模型,并对巢湖流域水资源系统脆弱性进行了综合评价。结果表明,巢湖流域水资源系统脆弱性为中度脆弱,各区域承载能力脆弱性均较高,但水资源脆弱性和生态环境脆弱性也不容忽视,应加强流域水资源综合治理,提高综合治理成效。     

A particle‐scale index in the quantification of mixing of particles

Discrete element method (DEM) is a useful tool for obtaining details of mixing processes at a particle scale. It has been shown to satisfactorily describe the flow structure developed in bladed mixers. Here, the advantage is taken of the microstructure gained from DEM to evaluate how best to quantify the microstructure created by mixing. A particle‐scale mixing index (PSMI) is defined based on coordination numbers to represent the structure of a particle mixture. The mixture quality is then analyzed qualitatively and quantitatively in three different ways: a macroscopic mixing index based on the conventional approach, coordination number, and PSMI. Their effectiveness is examined based on DEM data generated for different particle loading arrangements and binary mixtures of particles with various volume fractions, size ratios, and density ratios. Unlike the two other methods, PSMI reveals in a straightforward manner whether a binary mixture of different particles is mixing or segregating over time, while being able to detect particle‐scale structural changes accompanying the mixing or segregation processes in all the mixtures investigated. Moreover, PSMI is promising in that it is not influenced by the size and number of samples, which afflict conventional mixing indexes. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

基于Moldflow的解决LED显示屏前壳的翘曲问题

塑件翘曲变形问题一直是困扰注塑行业的一大问题,传统的解决方案是先制模然后通过反复试模来解决模具的翘曲变形问题。现在通过Moldflow模流分析软件可以精确的分析、预测塑件的翘曲变形,并通过预测结果来改变模具的设计结构和工艺条件最终优化模具。     

Microdroplet coalescences at microchannel junctions with different collision angles

Microdroplet coalescence mechanism is very important for the miniaturization of multiphase chemical processes with microstructured devices. Using three working systems with different physical properties, this article presents an experimental study on the fluid dynamics of microdroplet coalescence at different microchannel junctions. The critical capillary number to distinguish coalescence or noncoalescence of microdroplet is investigated and its variations with droplet size, collision angle, and physical properties are analyzed with two important parameters – the film drainage time and droplet contact time. Experimental results indicate that microdroplet coalescence can be enhanced by reducing the droplet collision angle. The differences of microdroplet coalescences in confined microchannels and free‐flowing spaces are provided with the analysis of critical capillary number. A model equation is proposed to predict the critical capillary numbers in this study, which may provide valuable information for the design and development of new microstructured chemical device. © 2012 American Institute of Chemical Engineers AIChE J, 59: 643–649, 2013     

An analytical solution to the extended Navier–Stokes equations using the Lambert W function

Microchannel gas flows are of importance in a wide range of microelectro mechanical devices. In these flows, the mean free path of the gas can be comparable to the characteristic length of the microchannel, leading to strong diffusion‐enhanced transport of momentum. Numerical solutions to the extended Navier–Stokes equations (ENSE) have successfully modeled such microchannel flows. Analytical solutions to the ENSE for the pressure and velocity fields using the Lambert W function are derived. We find that diffusive contributions to the total transport are only dominant for low average pressures and low pressure drops across the microchannel. For large inlet pressures, we show that the expressions involving the Lambert W function predict steep gradients in the pressure and velocity localized near the channel exit. We extract a characteristic length for this boundary layer. Our analytical results are validated by numerical and experimental results available in the literature. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1413–1423, 2014     

关于化学反应动力学方程的教学讨论

本文讨论了化学反应动力学方程的一般科学表示形式和反应物出现负级数的可能机制,指出在直链反应的化学反应动力学方程推导教学中应引入链传递过程的循环次数n。     

1-乙氧基-2-丙醇/水/癸烷的液液平衡

引　言石油是目前最重要的能源 ,除了液体石油外 ,油砂和油岩也能作为石油资源 .油岩分散存在于砂岩层中 ,只能通过物理的方法开采 ,乳化是可利用的提取方式之一 .为了了解乳化的原理及其体系的变化动态 ,作者曾经考察了 2 乙氧基乙醇、癸烷和水的液液三相平衡[1] .作为系统研     

Using CFD to predict the behavior of power law fluids near axial-flow impellers operating in the transitional flow regime

A computational fluid dynamics (CFD) model of flow in a mixing tank with a single axial-flow impeller was developed with the Fluent^TM software. The model consists of an unstructured hexagonal mesh (158,000 total cells), dense in the region from the surface of the impeller. The flow was modeled as laminar and a multiple reference frame approach was used to solve the discretized equations of motion in one-quarter of a baffled tank. A solution of 0.1% Carbopol in water, a shear-thinning fluid, was found to be clear enough to measure impeller discharge angles using laser Doppler velocimetry. This is the first time that impeller discharge angles have been reported in the literature for a shear-thinning fluid with a hydrofoil impeller. Rheological measurements indicated that the Carbopol solution can be characterized by the power law (K=9,n=0.2) under the range of shear conditions (0.1- expected near the impeller in the mixing tank. The CFD model accurately predicted the dependence of power number and discharge angle on Reynolds number (as predicted by Metzner and Otto), for an A200 (pitched blade turbine or PBT) and an A315 (Hydrofoil) impeller operating in the transitional flow regime (Reynolds numbers: 25-400) with glycerin and 0.1% Carbopol solutions. Subsequently, the results of a systematic CFD study with power law fluids indicated that the power number and discharge angle of an axial-flow impeller in the transitional flow regime depends not only on the Reynolds number (as determined by Metzner and Otto's method) but also on the flow behavior index n. Consequently, an alternative to Metzner and Otto's method was pursued. The results of converged CFD simulations indicate that the near-impeller “average shear rate” increases not only with increasing RPM (as proposed by Metzner and Otto), but also with decreasing flow behavior index (n) and discharge angle in the transitional flow regime. Considering this result, an improved method of estimating the power number and discharge angle for power law fluids in the transitional flow regime is proposed.