A reduced reaction mechanism for the simulation in ethylene flare combustion

Industrial ethylene flares are considered to be a probable major source of volatile organic compounds (VOCs) such as formaldehyde. VOCs are chemicals that are responsible for the formation of other atmospheric pollutants like ozone. Due to the difficulty and cost of field measurements, on-line monitoring is not practical and other methods must be employed. Current methodologies for calculating speciated and total VOC emissions from flaring activities generally apply a simple mass reduction to the VOC species sent to the flare that does not consider the production of incomplete combustion or other intermediates. There arises a need of a speciation study for the inspection of these flare for their emission. However, most of the detailed kinetic mechanisms for the speciation study of flaring events are too complex, consist of large number of reactions and species, and also are computationally expensive. A reduced mechanism will thus be desirable for improving computational efficiency. In this study, a reduced mechanism for simulating ethylene flare combustion is presented. By retaining the important features of the detailed mechanism in the form of elementary reactions, and satisfying the species constraint of commercial CFD packages, the reduced mechanism, thereby, is useful for speciation study of flaring event.     

Surface combustion microengines based on photocatalytic oxidations of hydrocarbons at room temperature

The concept of a surface combustion microengine that is fuelled by volatile hydrocarbons at room temperature is demonstrated on a microcantilever covered with a thin layer of titanium oxide (TiO(2)). Exposing this microengine to ultraviolet (UV) radiation and hydrocarbon vapor produces controlled bending of the microcantilever as a result of differential stress produced by photocatalytic oxidation of organic molecules on the TiO(2) coating. Compared to the motion generated solely by UV radiation or hydrocarbon adsorption, the unique photocatalytic-mechanical effects in the presence of UV and hydrocarbon produce more work and exhibit fast response. The surface combustion based microengines would require less maintenance in minimally controlled field environment and could be potentially used in construction of miniature movable machines, conversion of solar and chemical energy to mechanical work, when extended to a large array of microcantilevers. We believe such microengines can be fuelled by a variety of molecules or mixtures due to the generally favorable photocatalytic reactivity of TiO(2), thus potentially offering a broad approach for mechanical work generation from multiple energy sources.     

Calculation of the heats of combustion of aromatic hydrocarbons contained in power-generating fuel

The additive method of group contributions is used for the calculation of the heats of combustion of aromatic hydrocarbons of different structures.     

Validation of dynamic light scattering and centrifugal liquid sedimentation methods for nanoparticle characterisation

A variety of techniques exists to analyse the size and size distribution of nanoparticles in a suspension. However, these nanoparticle characterisation methods have been rarely fully validated and appropriate reference materials with properly assigned SI traceable values are not easily found. This paper presents results of in-house validation studies of Dynamic Light Scattering (DLS) and Centrifugal Liquid Sedimentation (CLS) methods. During these studies, a silica nanoparticle reference material was tested under repeatability and intermediate precision conditions. The trueness of the DLS and CLS methods was investigated by measuring gold and polystyrene nanoparticle reference materials. Furthermore, for each method, an uncertainty budget has been established. Both method validation and estimation of reliable measurement uncertainties are prerequisites for the certification of new nanoparticle reference materials.     

Polychlorinated naphthalenes and other chlorinated tricyclic aromatic hydrocarbons emitted from combustion of polyvinylchloride

Chloronaphthalenes (CNs) and phenanthrenes or/and anthracenes (CP/CAs) were detected in the emissions of polyvinylchloride (PVC) combustion at 900 degrees C. The presence of metallic iron, copper, or aluminum increased the formation of highly chlorinated CNs (tri- to octachloro-homologues) in the PVC combustion process. Total levels of CNs and CP/CAs were 40-48 and 76-116 mg/kg PVC, respectively, in the emissions from combustion of PVC with metals. Monochloronaphthalenes, dichloronaphtahlenes, monochlorophenanthrenes, and monochloroanthracenes were the predominant homologues. The other CN homologues were minor combustion byproducts. Detection of CNs in the PVC combustion emissions suggests that CN formation from solid waste incineration is a source of CNs in the environment.     

计及活塞销间隙的内燃机曲柄连杆机构动力学分析

基于活塞销与衬套间隙的冲击函数模型和计算多体动力学的方法,研究了活塞销间隙对内燃机活塞-连杆-曲轴运动系统动力学特性的影响。使用冲击函数方法构建了活塞销与衬套的间隙碰撞模型,建立了某单缸内燃机活塞、连杆和曲轴的三维实体模型及内燃机活塞-连杆-曲轴的多体动力学模型。在刚性和弹性两种不同连杆模型下,通过分析活塞运动的速度和加速度,以及活塞销的运动轨迹等研究了活塞销间隙产生的碰撞特性对系统动力学行为的影响。结果表明,间隙的存在对该运动机构有显著影响,在上下止点附近活塞的加速度出现许多由碰撞产生的峰值。     

Acoustic resonance determination of the effect of light hydrocarbons on wax appearance points in a Njord well fluid

Wax formation and deposition in pipelines and process equipment pose severe problems for petroleum companies. especially during transportation of crude oil in offshore environments. The light hydrocarbons present in the crude oil can play an important role in the shift of wax appearance points by increasing the solubilities of the heavier components. The following work was undertaken to study the effect of light hydrocarbons on wax appearance points in a Njord well fluid for Norsk Hydro, Norway. An automated high-pressure spherical acoustic resonator (50-mm-diameter) assembly designed and fabricated for that purpose has been used to measure resonance frequencies in a Njord well fluid (stabilized oil sample) provided by Norsk Flydro and blended with the appropriate amount of a synthetically prepared gaseous mixture containing six light hydrocarbons (CI to C6 ), at pressures from 2 to 107 bar and temperatures in the range 35 to 50 C. Results on the present method to locate the wax appearance points in the Njord well fluid are presented. A figure showing experimental wax appearance points as a function of pressure is presented. The results are compared with those predicted by the Norsk Hydro model.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994. Boulder, Colorado, USA.     

Two-fold mechanism of the interaction of incident light with a phase diffraction grating

It is suggested to use antireflection diffraction gratings for introducing light into the active regions of optoelectronic devices. The dependence of the diffraction efficiency on the grating groove depth, which controls the reflection from the optical surface and forms the diffraction order in the material, has been numerically modeled.     

Anionic NbO-type copper organic framework decorated with carboxylate groups for light hydrocarbons separation under ambient conditions

Light hydrocarbons are important raw materials for industrial products and fine chemicals. The storage and separation of C₁–C₃ hydrocarbons are vital to their practical use. Here, we report efficient C₁–C₃ hydrocarbon adsorption and separation with a NbO-type anionic copper metal–organic framework with uncoordinated –COO^? groups ([Cu₂(L)·(H₂O)₂]·2H₂O·3DMA·(CH₃)₂NH₂) (1). Complex 1 exhibited large C₂H₂ (190 cm³ g^?1), C₂H₄ (147 cm³ g^?1), C₂H₆ (156 cm³ g^?1), C₃H₆ (170 cm³ g^?1), and C₃H₈ (173 cm³ g^?1) uptakes and high selectivities for C₂H₂/CH₄ (32.3), C₃H₆/CH₄ (152), and C₃H₈/CH₄ (127) under ambient conditions. The excellent cycling performance of the material was reflected by only 9.2 and 10.9% losses of the C₂H₂ and C₃H₆ storage capacities even after ten cycles of adsorption–desorption tests. First-principles calculations and Grand canonical Monte Carlo simulations further revealed that not only the open metal sites but also the –COO^? groups played a key role in the high C₂–C₃ hydrocarbon uptakes. The results obtained in this study suggest that anionic 1 is a promising candidate for light hydrocarbon adsorption and natural gas purification at room temperature.     

The power-saving mechanism for solar power LED traffic signal light system

This article proposes a mechanism to reduce the battery power consumed by an independent solar-powered light intensity detection (LED) used for auxiliary traffic sign lighting by means of special background light sensor detection and an LED brightness control. This kind of traffic sign is deployed in remote areas and public utilities, where workers find hard to reach. Symbols and signs shaped by LED lights can assist drivers in mountain areas, remote areas, roads and highways with indications of directions and/or speed limits such that traffic accidents can be reduced. LED lights are especially suitable for environments with poor lights.     

内燃机主运动机构可靠性分析

 运用机构运动精度可靠性理论到内燃机主运动机构设计中,讨论了内燃机主运动机构运动精度可靠性分析问题．利用一阶Taylor展开方法推导机构运动精度误差表达式,并且引入可靠性理论建立了符合工程实际的极限状态函数表达式．在随机参数分布特性给定的情况下,通过计算机程序可以实现内燃机主运动机构的可靠性分析,迅速、准确地得到平面连杆机构运动精度可靠度．计算表明,所述方法是实用、有效的,具有重要的理论价值和实用意义．