Generation of excited electronic states at the nonmetal surface by the hydrogen atoms beam

The low energy excitation electronic states by the hydrogen atoms at the nonmetal surface are described using several possible mechanisms. The study results of the luminescence excited surface of the phosphor ZnS-Tm during interaction with H atoms are reported. Nonstationary with time the light intensity from ZnS-Tm is detected. This phenomenon interpreted on basis of the exchange-associative mechanism taking into account the acceleration of the surface recombination of hydrogen atoms in the adsorbed layer of the vibrationally excited hydrogen molecules. The rates of the absorption and recombination of hydrogen atoms and the desorption rate of the hydrogen molecules are defined. The possible mechanisms of excitation of the surface electronic states during interaction with the hydrogen low-energy atoms are discussed.     

An analysis of the electrical characteristics of DSC under inhomogeneous solar illumination

A simple model to describe the dye sensitized solar cell (DSC) is presented in which simultaneous occurrence of diffusion and charge transfer processes, power loss due to inhomogeneous excitation resulted from absorption of the dye and the electrolyte, and power gain due to the direct excitation (not via dye molecules) of semiconductor particles are taken into consideration. About 35% and 2.2% decrease in power is estimated for the dye and the electrolyte absorption, respectively, while 2.9% increase of power is obtained by the direct excitation of TiO₂ at maximum power point (MPP) under AM1.5 solar illumination. Some numerical results are also presented to demonstrate the influence of the material parameters for the cell characteristics.     

Investigation on the mass entrainment of an acoustically controlled elliptic jet

The mass entrainment of the elliptic jet under acoustic excitations with fundamental and subharmonic frequency were investigated experimentally in this paper. Results show that the azimuthal deformation increases the interfacial area and engulfs more fluid from surrounding into the free shear layer, it implies the azimuthal deformation plays an important role in the mass transfer of an elliptic jet. Results also reveal that most of the entrainment occurs around the minor-axis plane, but the mass can be entrained significantly around the major-axis plane when the elliptic jet under the subharmonic frequency excitation, i.e., f_e (f₀ /2, f₀ /2). It proposes that the subharmonic frequency excitation is effective to increase the mass entrainment of the elliptic jet.     

喷油矢量对柴油机曲轴扭振影响的机理

采用基于集中质量法的GT-SUITE软件,建立8,V2015柴油机曲轴系统动力学与性能协同仿真模型,并对其进行必要的试验标定.开展喷油矢量对柴油机曲轴扭振的影响机理的仿真研究,并以干扰力矩矢量和这一扭振能量衡量指标进行验证.结果表明,调节气缸循环喷油量影响发动机激励力矩低频段幅值,调整喷油提前角则主要影响中高频段的幅值和相位.激励力矩的影响机理可用来抑制曲轴扭振,不同喷油矢量的调节方案表明扭振抑制的有效性,其中减振器惯性体端5.5谐次的扭转角位移幅值降低21.2%;干扰力矩矢量和与扭转角位移的变化趋势一致,可作为扭振强弱的衡量指标以及扭振抑制的优化目标.     

EXPERIMENTAL STUDY ON PLASMA-ASSISTED MASS CONVERSIONS OF CO2 PURE AND (CO2 + H2) MIXTURE MOLECULES

Experimental trials have been carried out on plasma-assisted mass conversions associated with carbon dioxide, which is too stable to react chemically under normal conditions. First, pure gas molecules of CO were charged into a plasma reaction furnace containing a dc 2 glow discharge field between two electrodes of a circular anode and cathode emitting thermal electrons, and the mass-converted species and their respective yields measured by a combined time-of-flight and mass spectrometer technique. Second, mixture molecules of CO2 and H were also tested to seek a possibility of mass conversions into fuel-like species such as CO, CH . CH OH, etc. The experimental results proved that pure CO molecules are 4 3 2 well decomposed into CO with a relatively high yield and that mixture molecules of CO and 2 H are also able to well compose CH , CH OH, etc., with fairly good yields. As a result, 2 4 3 plasma is found to be of great help in promoting direct mass conversions with high efficiency.     

Measurements of the slow drift dynamics of a model Pelamis wave energy converter

The Pelamis wave energy converter (WEC) is moored with a clump-assisted wire catenary of high compliance that, coupled with the displacement mass of Pelamis, has a resonant frequency an order of magnitude lower than the wave frequencies. The mooring is thus decoupled from first-order wave excitation, and is excited by second-order slowly varying drift forces, which are mainly due to the wave momentum transferred to the device as wave power is absorbed. The slow drift motion is damped by a combination of drag and wave-drift damping. This paper describes an experimental investigation of the slow-drift excitation and damping.     

漂浮摆式波浪能发电装置的频时域仿真分析

文章研究了3种不同外形（圆、椭圆和椭圆-圆）波浪能发电装置的纵摇运动,通过ANSYS AQWA对3种外形装置进行了频域仿真,对比了3种外形装置的辐射阻尼、附加质量和波浪激励力等水动力系数;再将频域分析中得到的水动力系数导入WEC-SIM,进行了时域仿真,对比了3种外形装置的摆角和瞬时功率。研究结果表明,尽管椭圆形装置的辐射阻尼、附加质量和波浪激励力矩等水动力系数最大,但椭圆-圆形装置的摆角和瞬时功率最大,说明了不对称结构更有利于波浪能量的吸收和转化。     

Flame-vortex interaction and mixing behaviors of turbulent non-premixed jet flames under acoustic forcing

This study examines the effect of acoustic excitation using forced coaxial air on the flame characteristics of turbulent hydrogen non-premixed flames. A resonance frequency was selected to acoustically excite the coaxial air jet due to its ability to effectively amplify the acoustic amplitude and reduce flame length and NO_x emissions. Acoustic excitation causes the flame length to decrease by 15% and consequently, a 25% reduction in EINO_x is achieved, compared to coaxial air flames without acoustic excitation at the same coaxial air to fuel velocity ratio. Moreover, acoustic excitation induces periodical fluctuation of the coaxial air velocity, thus resulting in slight fluctuation of the fuel velocity. From phase-lock PIV and OH PLIF measurement, the local flow properties at the flame surface were investigated under acoustic forcing. During flame-vortex interaction in the near field region, the entrainment velocity and the flame surface area increased locally near the vortex. This increase in flame surface area and entrainment velocity is believed to be a crucial factor in reducing flame length and NO_x emission in coaxial jet flames with acoustic excitation. Local flame extinction occurred frequently when subjected to an excessive strain rate, indicating that intense mass transfer of fuel and air occurs radially inward at the flame surface.     

Effect of surface diffusion on transfer processes in heterogeneous systems

The paper presents a review of publications concerned with the influence of surface diffusion of adsorbed molecules on the course of processes in heterogeneous systems. The influence of resonance (in particular, laser) radiation on mass transfer in channels (porous bodies) with allowance for surface diffusion of adsorbed molecules is discussed.     

叶片缘板阻尼结构参数敏感特性分析

针对某型船用燃气轮机高压涡轮叶片的缘板阻尼结构设计问题,开展阻尼结构参数敏感性分析。基于整体-局部统一滑动理论建立叶片-阻尼单接触对摩擦模型,采用谐波平衡法和能量法将非线性摩擦力等效线性化;考虑激振力相位差,迭代求解振动微分方程以获得叶尖幅值响应,找出影响阻尼减振效果的关键参数,分辨具有高敏感度的独立变量,获取阻尼结构初步设计方案。结果表明：缘板阻尼器的质量与刚度、阻尼选材及接触面宽度均属于高敏感度参数;阻尼器所受离心力与激振力幅值之比可作为结构设计过程中的独立变量;计算得到阻尼器设计质量在1.18~3.95 g之间,阻尼器轴向设计长度为31.2 mm。     

Plasmochemical methods of hydrogen production

Hydrogen production in plasma is examined both in a one-stage process of water vapor decomposition and in a double-stage process with preliminary CO₂ destruction. Hydrogen production is considered in H.F. and U.H.F. moderate pressure gas discharges and in a non-self-sustained gas discharge stimulated by a relativistic electron beam. The high efficiency attained in U.H.F. discharge of CO₂ dissociation is explained by non-equilibrium vibrational excitation of CO₂ molecules in plasma.     

Modeling and Dynamic Simulations of Doubly Fed Adjustable-Speed Pumped Storage Units

This paper derives the mathematical models of doubly fed adjustable-speed pumped storage units (DFASPSUs) to be utilized in the power system analysis. It adopts the improved induction machine model with ac excitation on the wire-wound rotor as well as the field-oriented control theory for the study and analysis of DFASPSU models. First, the rotor excitation voltage is separated into two components, i.e., the q-axis voltage and the d-axis voltage, so as to control the output active and reactive powers, respectively. Next, a dynamic model of DFASPSU is derived using the swing equation of rotary electric machine and the equation of motion of rotor rotating mass. Finally, computer simulation is carried out to compare its results with practical examples in terms of dynamic characteristics for verifying the correctness of the proposed models.     

Influences of pressure amplitudes and frequencies of dual-frequency acoustic excitation on the mass transfer across interfaces of gas bubbles

In the present paper, the influence of pressure amplitudes and frequencies of dual-frequency acoustic excitation on the mass transfer across interfaces of gas bubbles are numerically investigated. The size of bubble growth region is proposed as a criterion for the optimization of the dual-frequency approach. Our simulation reveals that a. there exists a particular point at which the threshold of mass transfer is independent of the power allocation between two sonic waves; b. for the promotion of the effects of mass transfer, more energies should be allocated to the low-frequency sonic wave rather than the high-frequency sonic wave; and c. the benefits of dual-frequency approaches decrease with the increase of the frequency ratio of the two sonic waves.     

The promotion of ignition in a supersonic H2-air mixing layer by laser-induced excitation of O2 molecules: Numerical study

A possibility of a considerable enhancement of ignition in a diffusion mode in a supersonic non-premixed H₂-air flow by means of the laser-induced excitation of O₂ molecules to the electronic state is investigated on the base of numerical simulation. It is shown that for significant shortening the induction zone length it is sufficient to expose only a thin air layer (with thickness of 1-2 cm) to resonance laser radiation with a small input radiation energy 5 × 10⁻³-2 × 10⁻² J/cm³. Even a small amount of radiation energy transmitted to the air flow makes it possible to arrange a stable combustion at a short distance (?1 m) from the irradiation region at a relatively low temperature of the air (T = 800 K). Shortening the induction zone length, in this case, is due to intensification of chain-branching via excitation of O₂ molecules by laser radiation and penetration of excited molecules into the shear layer.     

Fluid thermal stratification in a non-isothermal liquid hydrogen tank under sloshing excitation

To the safe space operation of cryogenic storage tank, it is significant to study fluid thermal stratification under external heat leaks. In the present paper, a numerical model is established to investigate the thermal performance in a cryogenic liquid hydrogen tank under sloshing excitation. The interface phase change and the external convection heat transfer are considered. To realize fluid sloshing, the dynamic mesh coupled the volume of fluid (VOF) method is used to predict the interface fluctuations. A sinusoidal excitation is implemented via customized user-defined function (UDF) and applied on tank wall. The grid sensitivity study and the experimental validation of the numerical mode are made. It turns out that the present numerical model can be used to simulate the unsteady process in a non-isothermal sloshing tank. Variations of tank pressure, liquid and vapor mass, fluid temperature and thermal stratification are numerically investigated respectively. The results show that the sinusoidal excitation has caused large influence on thermal performance in liquid hydrogen tank. Some valuable conclusions are arrived, which is important to the depth understanding of the non-isothermal performance in a sloshing liquid hydrogen tank and may supply some technique reference for the methods of sloshing suppression.     

A model of particle nucleation in premixed ethylene flames

A detailed model of particle inception is proposed to delve into the physical structure and chemistry of combustion-formed particles. A sectional method is used, from a previously developed kinetic mechanism of particle formation with a double discretization of the particle phase in terms of C and H atom number. The present model also distinguishes between different particle structures based on their state of aggregation; single high molecular mass molecules, cluster of molecules and aggregates of clusters. The model predicts the mass of particles, hydrogen content and internal structure. It represents a first approach in following the chemical evolution and internal structure of the particles formed in flames, coupled with the main pyrolysis and oxidation of the fuel.The model is tested in atmospheric premixed flat flames of ethylene and the effect of fuel equivalence ratio on particle morphology is analyzed. Molecular weight growth of aromatic compounds and the inception of particles are predicted. The morphology of the particles and the number of molecules in the clusters at particle inception are also indicated.     

梯级泵站管道TMD振动控制仿真与减振优化

为了解调谐质量阻尼器(TMD)的减振效果,以某灌区泵站输水管道为例,全面分析TMD减振系统对管道结构的减振效果,以寻求最佳减振方案。结果表明,TMD减振系统可有效降低管道振动幅值;在适宜的质量比范围内,TMD减振效果相似;等质量情况下,单个TMD和两个TMD减振装置减振效果基本一致,因此在减少大质量附加质量对主结构自重的影响下,实际应用中宜分成等质量的多个减振装置,以达到较好减振效果;TMD装置布置在激励源附近或发生振动较明显的部位可高效减振。研究成果为大型管道结构振动原因分析和TMD减振控制产品研发提供了依据。     

Application of optical spectroscopy for investigation of synthesis of hydrogen and nanoparticles in electric discharge in liquid-phase media

In this work, a low-temperature plasma initiated in liquid media between electrodes has been shown to be able to decompose hydrogen containing organic molecules resulting in obtaining gaseous products with volume part of hydrogen higher than 90% as well as nanoparticles of discharge electrodes material. As feedstocks, organic compounds (alcohols, esters) as well as direct water-hydrocarbon emulsions obtained by ultrasonic treatment are used. It is shown that hydrogen productivity from emulsions is not less than that from individual substances.The method of optical spectroscopy was used to confirm the formation of atomic hydrogen in the reactions of plasma decomposition of liquids and to study of plasma characteristics in this process.The measurement of the amount of the gas mixture and nanosized products formed during the decomposition of organic liquids shows that the output is highly dependent on the discharge current, and also on the volume of the discharge, which can vary depending on the distance between the electrodes in the reaction chamber.The dependence of the glow intensity of the discharge on its parameters and materials of the discharge electrodes is shown. In current experiments, the discharge current is from 4A to 8A, the discharge voltage depending on the type of liquid is 30–45 V.It has been found that the simultaneous excitation of an electric arc discharge and acoustic cavitation in water, organic liquids and their mixtures is an effective method for the synthesis of gaseous hydrogen and various types of solid nanoparticles.Ultrasonic action above the cavitation threshold intensifies heat and mass transfer processes in the treated medium, promotes the homogenization of dispersed systems, activation of the surface of solid particles, the appearance of defects in crystal structures due to dislocations and the formation of vacancy complexes, in combination with an electric discharge, which contributes to the appearance of an ionized state of matter (plasma); such an effect is capable of decomposing complex molecules to an atomic state with subsequent recombination and the formation of simple molecules.It has been shown that this is an energetically favorable method for the conversion of liquid-phase compounds, stimulated by thermally nonequilibrium plasma, which produces active particles – excited molecules and radicals, which makes it possible to initiate chain reactions, including energetically branched ones, and thereby significantly accelerate the process of liquid conversion and decrease the temperature allowing for such conversion.Synthesized metal and metal oxide nanoparticles from electrode materials possess activated surface due to the ultrasonic cavitation and can be subsequently used as functional nanoparticles, e.g. nanoparticles with antibacterial properties as well as components of polymer composite materials.     

考虑流固耦合的泵站压力管道激振特性有限元分析

为探究大型高扬程泵站压力管道运行时高频激振的诱因和振动特性,以甘肃省景电二期总干七泵#1压力管道为研究对象,采用附加水体质量法建立基于ANSYS有限元的简化流固耦合仿真模型,对压力管道的激振特征进行数值模拟,分析不同机组启闭工况下压力管道的振动模态及位移变形规律,揭示压力管道的主要振动变形特性。结果表明,在多种运行工况下,压力管道弯管段和大小管连接段振动比较明显,且高阶模态的振型振幅高于低阶模态,不易被激振的出水管随着阶次的增高也逐渐产生振动变形。经DASP测试系统现场振动监测表明,数值模拟结果与现场测试结果吻合良好。该结论可为高扬程泵站压力管道避振、减振优化设计提供技术支撑,也为同类泵站工程的更新改造设计和安全运行提供理论依据。     

Dye-sensitization of magnesium-oxide-coated cadmium sulfide

Nanocrystalline films of cadmium sulfide sensitized with ruthenium N3 dye show only a feeble photoresponse either in the absorption region of the dye or the band gap excitation of cadmium sulfide. However, when an ultrathin outer shell of magnesium oxide is deposited on the cadmium sulfide crystallites in the film, the photoresponse in both the above regions of the spectrum are greatly enhanced. The result is explained as electron injection from excited dye molecules on the outer magnesium oxide shell to the conduction band of cadmium sulfide and suppression of the leakage of the relaxed electrons to the interface by the magnesium oxide barrier, where they undergo recombinations. Possible applications of this effect in dye-sensitized solar cells are discussed.