气体滤波相关技术在红外甲烷监测系统中的应用

针对空气痕量气体中甲烷含量低、吸收弱,在非分散红外甲烷检测系统中噪声干扰大的问题,本文提出了利用气体滤波相关检测技术去除背境噪声干扰来提高检测能力的方法.该方法依据气体对红外辐射的特征吸收和相关运算的原理,结合了先进的气体滤波技术和相关检测技术,实现了对微弱光谱信号的调制和检测,最后实现了对浓度的反演,从而达到了甲烷气体实时、快速在线检测目的.试验结果表明,系统有10 ppb的测量精度.     

便携式摩托车尾气分析仪的研制

介绍了自行研制的利用工业计算机主板实现的新型便携式摩托车尾气分析仪.该分析仪由采样系统、气体分析系统、辅助测量系统和显示系统组成.使用非扩散红外线(NDIR)光吸收方法分析HC、CO和CO2质量分数;使用电化学方法分析O2和NOx质量分数;采用磁电式感应器测量摩托车速度;热线式气体流量计测量尾气的流量.系统包括工业计算机主板、气体传感器、转速传感器、LCD显示屏、液晶屏、气体流量计、微型打印机等硬件部分和软件设计.研制的摩托车尾气分析仪能测量摩托车在各工况下的尾气排放状况.     

Design optimization of a prescribed vibration system using conjoint value analysis

This article details a novel design optimization strategy for a prescribed vibration system (PVS) used to mechanically filter solids from fluids in oil and gas drilling operations. A dynamic model of the PVS is developed, and the effects of disturbance torques are detailed. This model is used to predict the effects of design parameters on system performance and efficiency, as quantified by system attributes. Conjoint value analysis, a statistical technique commonly used in marketing science, is utilized to incorporate designer preferences. This approach effectively quantifies and optimizes preference-based trade-offs in the design process. The effects of designer preferences on system performance and efficiency are simulated. This novel optimization strategy yields improvements in all system attributes across all simulated vibration profiles, and is applicable to other industrial electromechanical systems.     

相关检测技术在CO气体监测系统中的应用

相关检测技术是实现微弱信号检测的重要方法。本文介绍了该技术在非分散红外CO气体监测系统中的应用,根据相关检测理论,设计了同步相关检测电路,成功地实现了信号和噪声的分离度。实验表明,设计的基于相关检测的CO监测系统在0~200ppm的测量范围内有10ppb的监测精度。     

Applications of modeling in polymer-property prediction

Summary A number of molecular modeling techniques have been applied for the prediction of polymer properties and behavior. Five examples illustrate the range of methodologies used. A simple atomistic simulation of small polymer fragments is used to estimate drug compatibility with a polymer matrix. The analysis of molecular dynamics results from a more complex model of a swollen hydrogel system is used to study gas diffusion in contact lenses. Statistical mechanics are used to predict conformation dependent properties — an example is the prediction of liquid-crystal formation. The effect of the molecular weight distribution on phase separation in polyalkanes is predicted using thermodynamic models. In some cases, the properties of interest cannot be directly predicted using simulation methods or polymer theory. Correlation methods may be used to bridge the gap between molecular structure and macroscopic properties. The final example shows how connectivity-indices-based quantitative structure-property relationships were used to predict properties for candidate polyimids in an electronics application.     

Characterization of a mid-infrared hollow waveguide gas cell for the analysis of carbon monoxide and nitric oxide

Infrared spectroscopy is commonly applied to the analysis of small gas-phase molecules. One of the limitations of using Fourier transform infrared (FT-IR) spectroscopy for these applications is the time response of long path length gas cells. Hollow waveguides (HW) that transmit in the mid-infrared spectral range have higher optical efficiencies compared to long path length cells due to smaller cell volumes. This study characterizes a silver coated, 2 mm inner diameter HW for the analysis of carbon monoxide (CO) and nitric oxide (NO) and compares the performance to a 3 m gas cell and traditional gas analyzers. The HW was found to have a CO response time less than the NDIR analyzer and approximately one-tenth of the response time on the FT-IR system equipped with a 3 m gas cell. The utility of the increased response time was demonstrated by measuring CO concentrations in sidestream cigarette smoke at the same temporal resolution as an NDIR analyzer. A 10 to 60% increase in sensitivity using various frequencies for both CO and NO was observed using the HW compared to the 3 m multipass gas cell. However, cost savings for gas-sensing applications can be achieved on a per analyte basis by using FT-IR spectroscopy, especially in combination with a HW gas-sensing module, which is significantly less expensive than a multipass gas cell.     

非分散红外吸收光谱法空气痕量污染气体监测浓度算法

针对城市痕量污染气体检测中,所测气体浓度低、吸收弱,采用两点标定和高浓度标气定标造成吸收曲线误差增大的问题,本文提出了采用低浓度标气.多点定标的方法来获得吸收曲线的方法来建立吸收方程.该方法是基于比尔-朗伯吸收定律的吸收方程,当测量气体浓度较低时,其浓度和吸光度呈线性关系来完成.采用低浓度标气.多点定标两种方法的结合,来获得测量气体的吸收曲线.试验结果表明,有很高的测量精度.     

Experimental study and particle population modeling of coating in a jet-fluidized bed

The present work focuses on the study of a bottom-spray fluidized-bed coater in the absence of any liquid (solvent) evaporation. The main objective is to point out and model the effect of operating conditions on the coating efficiency and the coating mass content distribution of particles. A fluidized bed with a bottom-placed spraying nozzle situated in the middle of a perforated distributor plate was used. The experimental results showed that increasing the jet and fluidizing gas flow rates improve the quality of coating, but there is a limitation for the binder flow rate which is dependent on the bed size and jet gas flow rate. Based on the experimental results, an empirical function was derived to predict the coating efficiency in different operating conditions and this function was also used in the mathematical model. Furthermore, a mathematical model was derived based on the population balance equations for two different zones in the bed. The model could predict the coating mass content distribution and the effect of different operating conditions during the process.     

红外吸收光谱（NDIR）检测混合气体中二甲醚含量分析法

利用非分光红外吸收光谱法（NDIR）,采用中红外光源（波长：2．5—25μm）和主要包括样品气气阻、样品泵、红外吸收池和电路模块技术建立了混合气体中二甲醚气体成分光谱检测系统,并使用该系统对混合气体中的二甲醚气体成分进行了测量,得到了1．0×10^-2的检测灵敏度。整个光谱检测系统具有很好的光谱分辨率、选择性以及测量灵敏度,适用于各种混合气体中二甲醚气体成分的检测。     

Computational modeling of explosive-filled cylinders

A time-dependent, two-dimensional, finite-difference code can be used to model fragmenting cylinders. Strictly hydrodynamic treatment of the casing material generally overpredicts the final fragment velocity. A more definitive final fragment velocity is predicted when the casing material is treated as an elastic-plastic material, but the final fragment velocities occur at unrealistically high cylindrical expansion ratios. To remove some of these objections and, at the same time, model the casing motion more realistically, a gas leakage model has been developed to simulate explosive gas leakage around fragments after casing breakup. Comparisons have been made between code calculations and experimental data. The experimental data include different length-to-diameter ratios, natural and discrete fragmenting cylinders, different charge-to-casing mass ratios, and different initiation postures. The gas leakage model predicts definitive final fragment velocities in excellent agreement with the experimental data.     

Application of ESP for gas cleaning in cement industry--with reference to India

Electrostatic precipitators (ESP) are used for gas cleaning in almost every section of cement manufacture. Application of ESP is studied, keeping in view Indian conditions. The characterisation of dust emissions has been done for different units, such as rotary kiln and raw mill, alkali by-pass, clinker cooler, cement and coal mill, in terms of exit gas quantity, temperature, dew point, dust content and particle size. It is seen that all these characteristics have a wide range of variance. The ESP system must effectively deal with these variations. The fundamental analytical expression governing the performance of ESP, i.e. the Deutsch equation, and that for particle migration velocity, were analysed to predict the effect of major operating parameters, namely particle size, temperature and applied voltage. Whereas the migration velocity (and the efficiency) varies directly with the particle size, it is proportional to the square and square root of applied voltage and absolute temperature of the gas, respectively. The increase in efficiency due to temperature is not seen in dc based ESP, perhaps due to more pronounced negative effect on the applied voltage due to the increase in dust resistivity at higher temperatures. The effect of gas and dust characteristics on the collection efficiency of ESP, as seen in the industrial practice, is summarised. Some main process and design improvements effectively dealing with the problem of gas and dust characteristics have been discussed. These are gas conditioning, pulse energization, ESP-fabric filter (FF) combination, improved horizontal flow as well as open top ESP.Generally, gas conditioning entails higher operating and maintenance costs. Pulse energization allows the use of hot gas, besides reducing the dust emission and power consumption. The improved horizontal flow ESP has been successfully used in coal dust cleaning. The open top or vertical flow ESP has a limitation on collection efficiency as it provides for only one electric field.     

能量分析器型真空电离规性能研究

电子激励脱附(ESD)效应和软X射线效应是影响电离真空计测量下限的两大重要因素。基于能量分析器研制了电离真空规,在极高真空校准装置上对其开展性能研究,包括不同压力或不同阴极发射电流下的离子流、ESD效应和软X射线影响。结果表明,系统压力介于10^-8 Pa和10^-6 Pa之间,当气体发生电离,能量分析器电压在低于阳极电压约25 V时收集极能得到最大的气相离子流。系统压力在10-7~10^-8 Pa量级,采用2.5 mA的发射电流可得到比1 mA更大的气相离子流值。分离气相离子与ESD离子的能量筒电压差约为30 V,规管栅极除气后可降低ESD效应至除气前的37.5%。电离规的软X射线带来的本底干扰对应等效压力约为9×10^-11 Pa。     

Hot-gas flow and particle transport and deposition in a candle filter vessel

Hot-gas flow and particle transport and deposition in an industrial filtration system are studied. The special example of the Siemens-Westinghouse filter vessel at the Power System Development Facility at Wilsonville, Alabama is treated in detail. This tangential flow filter vessel contains clusters of 91 candle filters, which are arranged in two tiers. The upper tier containing 36 candle filters is modeled by six equivalent filters. Seven equivalent filters are used in the computational model to represent the 55 candle filters in the lower tiers. The Reynolds stress turbulent model of FLUENT™ code is used, and the gas mean velocity and root mean square fluctuation velocities in the filter vessel are evaluated. The particle equation of motion used includes drag and gravitational forces. The mean particle deposition patterns are evaluated and the effect of particle size is studied. The computational results indicatethat large particlesof the order of 10 μm or larger are removed from the gas due to the centrifugal forces exerted by rotating flow between the shroud and the refractory.     

3D CFD-PBM modeling of the gas–solid flow field in a polydisperse polymerization FBR: The effect of drag model

This work investigated a coupled computational fluid dynamics and population balance modeling (CFD-PBM) approach to predict the hydrodynamic behavior of the complex gas–solid two-phase flow in a three-dimensional (3-D) polydisperse propylene polymerization fluidized bed reactors (FBRs). Four different drag models, namely Syamlal–O’Brien, Gidaspow, McKeen and EMMS, were incorporated into the CFD-PBM model for evaluating the different effect of drag force between the gas and solid phases. Simulation results revealed a significant effect of the drag model on gas–solid flow in polydisperse polymerization FBRs. It was found that (1) compared to Syamlal–O’Brien and Gidaspow drag models, McKeen and EMMS drag models could predict a lower bed height, a higher temperature and an obvious core-annulus structure in polymerization FBRs; (2) EMMS drag model outperforms the other three drag models with respect to pressure drop prediction; and (3) the drag coefficient had little influence on the evolution of Sauter number and particle-size distribution.     

NUMERICAL CALCULATION OF PARTICLE COLLECTION IN ELECTRICALLY ENHANCED FIBROUS FILTERS

The collection of particles In an electrostatically enhanced fibrous filter Is Investigated numerically. Individual particle pathlines are computed within a model filter. The model filter Is composed of an array of parallel cylinders arranged In a regular pattern. The effect of such forces as electrophoresis, dielectrophoresis, Brownian motion, and particle Inertia Is considered. It Is shown that the model can predict the Influence of these forces on the collection efficiency of a fibrous filter, and that the model Is able to match available data of enhanced collection to a reasonable degree of accuracy.     

NUMERICAL CALCULATION OF PARTICLE COLLECTION IN ELECTRICALLY ENHANCED FIBROUS FILTERS

The collection of particles In an electrostatically enhanced fibrous filter Is Investigated numerically. Individual particle pathlines are computed within a model filter. The model filter Is composed of an array of parallel cylinders arranged In a regular pattern. The effect of such forces as electrophoresis, dielectrophoresis, Brownian motion, and particle Inertia Is considered. It Is shown that the model can predict the Influence of these forces on the collection efficiency of a fibrous filter, and that the model Is able to match available data of enhanced collection to a reasonable degree of accuracy.     

Cold roll bonding of multi-layered bi-metal laminate composites

Multi-layered laminate composites of dissimilar metals have assumed importance industrially. Cold roll bonding can produce multi-layered sheet composites. Study of the effect of rolling and material variables on the bonding characteristics needs to be studied in order to predict the optimum bonding conditions and the final composition of the laminate sheets. In this work, cold roll bonding of multi-layered bimetals has been modeled using the slab method. The effect of anisotropy has been included. Effects of different process and material variables are analyzed. Novel experiments were performed on multilayered Ti–Al system and the numerical results from the model were compared with the experimental results. A good agreement was observed between the model and experimental results.     

Computational modelling of turbulent flow,combustion and heat transfer in glass furnaces

For the combustion of natural gas in high temperature glass furnaces a computational model “Furnace” has been developed. It includes 3-D turbulent flow, flame chemistry, radiative heat transfer and the formation of soot and of the pollutant NO. Turbulent fluctuations have been taken into account, and are shown to have a large effect on thermal radiation and NO-formation. Spectral behaviour of gas radiation results in changes of heat transfer efficiency up to 5%, depending on refractory emissivity. The model has been employed to predict NO formation for different burner geometries. In general, a decrease in mixing of gas and air results in a reduction of 1600 to 400 ppm in flue gas NO concentration. Except for some of the low mixing flames, however, they lead to a lower burnout and a very high CO level in the flue gas. A comparison with semi-technical furnace tests shows that the model can predict NO formation reasonably well. With this computational model the designer of furnaces and burners can study further possibilities for increased furnace performance and low NO emissions.     

基于AdaBoost的多项式旋流器溢流粒度软测量模型

为了降低选矿的生产成本和维护成本,提出了基于AdaBoost的多项式旋流器溢流粒度软测量模型。该模型以均方误差最小化为目标函数建立多项式模型,采用AdaBoost加强性能较差的样本的训练提高模型的泛化性和精度。最后将多个模型按照不同的权重集成起来作为最终模型。模型仿真和工业现场的实际应用效果说明,该模型能够比较准确地预测旋流器溢流粒度,保证了水利旋流器溢流粒度的合格率,提高了选矿效率,具有一定的实用性。