Bidirectional rotating direct-current triboelectric nanogenerator with self-adaptive mechanical switching for harvesting reciprocating motion

Amid the growing interest in triboelectric nanogenerators(TENGs)as novel energy-harvesting devices,several studies have focused on direct current(DC)TENGs to generate a stable DC output for operating electronic devices.However,owing to the working mechanisms of conventional DC TENGs,generating a stable DC output from reciprocating motion remains a challenge.Accordingly,we propose a bidirectional rotating DC TENG(BiR-TENG),which can generate DC outputs,regardless of the direction of rotation,from reciprocating motions.The distinct design of the BiR-TENG enables the mechanical rectification of the alternating current output into a rotational-direction-dependent DC output.Furthermore,it allows the conversion of the rotational-direction-dependent DC output into a unidirectional DC output by adapting the configurations depending on the rotational direction.Owing to these tailored design strategies and subsequent optimizations,the BiR-TENG could generate an effective unidirectional DC output.Applications of the BiR-TENG for the reciprocating motions of swinging doors and waves were demonstrated by harnessing this output.This study demonstrates the potential of the BiR-TENG design strategy as an effective and versatile solution for energy harvesting from reciprocating motions,highlighting the suitability of DC outputs as an energy source for electronic devices.

Constructions and Preliminary HV Conditioning of a Photocathode Direct-Current Electron Gun at IHEP

As one of the most important key technologies for future advanced light source based on the energy recovery linac, a photocathode dc electron gun is supported by Institute of High Energy Physics （IHEP） to address the technical challenges of producing very low ernittance beams at high average current. Construction of the dc gun is completed and a preliminary high voltage conditioning is carried out up to 440 k V. The design, construction and preliminary HV conditioning results for the dc gun are described.

Anomalous Direct-Current Josephson Effect in Semiconductor Nanowire Junctions

We investigate the dc Josephson effect in one-dimensional junctions where a ring conductor is sandwiched between two semiconductor nanowires with proximity-induced superconductivity. Peculiar features of the Josephson effect arise due to the interplay of spin-orbit interaction and external Zeenmn field. By tuning the Zeeman field orientation, the device can vary from 0 to π junction. Afore importantly, nonzero ,losephson current is possible at zero phase difference across the junction. Although this anomalous Josephson current is not relevant to the topological phase transition, its magnitude can be significantly enhanced whe, n the nanowire, s become topological superconductors where Majorana bound states emerge. Distinct modulation patterns are obtained for the semiconductor nanowires in the topologically trivial and non-trivial phases. These results are useful to probe the topological phase transition in semiconductor nanowire junctions via the dc Josephson effect.

Modeling of Pulsed Direct-Current Glow Discharge

A self-consistent model was adopted to study the time evolution of low-voltage pulsed DC glow discharge. The distributions of electric field, ion density and electron density in nitrogen were investigated in our simulation, and the temporal shape of the discharge current was also obtained. Our results show that the dynamic behaviors of the discharge depends strongly on the applied pulse voltage, and the use of higher pulse voltages results in a significantly increase of discharge current and a decrease of discharge delay time. The current-voltage characteristic cMculated by adjusting secondary electron emission coefficient for different applied pulse voltage under the gas pressure of 1 Torr is found in a reasonable agreement with the experimental results.

Effects of the sputtering power on the crystalline structure and optical properties of the silver oxide films deposited using direct-current reactive magnetron sputtering

This paper reports that a series of silver oxide （AgzO） films are deposited on glass substrates by direct-current reactive magnetron sputtering at a substrate temperature of 250 ℃ and an oxygen flux ratio of 15：18 by modifying the sputtering power （SP）. The AgxO films deposited apparently show a structural evolution from cubic biphased （AgO ＋ Ag20） to cubic single-phased （Ag20）, and to biphased （Ag20 ＋ AgO） structure. Notably, the cubic single-phased Ag20 fihn is deposited at the SP = 105 W and an AgO phase with （220） orientation discerned in the Ag^O films deposited using the SP 〉 105 W. The transmissivity and refiectivity of the AgxO films in transparent region decrease with the increase the SP, whereas the absorptivity inversely increases with the increase of the SP. These results may be due to the structural evolution and the increasing film thickness. A redshift of the films＇ absorption edges determined in terms of Tauc formula clearly occurs from 3.1 eV to 2.73 eV with the increase of the SP.

Research on corona discharge suppression of high-voltage direct-current transmission lines based on dielectric-film-covered conductor

Corona discharge suppression for high-voltage direct-current(HVDC)transmission lines at line terminals such as converter stations is a subject that requires attention.In this paper,a method based on a conductor covered with dielectric film is proposed and implemented through a bench-scale setup.Compared with the bare conductor,the corona discharge suppression effect of the dielectric-film-covered conductor under positive polarity is studied from the composite field strength and ion current density using a line-plate experimental device.The influences of film thickness and film material on the corona discharge suppression effect are investigated.The charge accumulation and dissipation characteristics of different film materials are also studied.The results show that the conductor covered with dielectric film has excellent ability to inhibit corona discharge.The ground-level composite field strength of the conductor covered with dielectric film is lower than its nominal field strength,and its ion current density is at the nA m^(−2) level.The corona threshold voltage can be promoted by increasing the film thickness,but the ability to inhibit corona discharge becomes weak.The larger the surface electric field strength,the more charge accumulated,but the faster the charge dissipation rate.Compared with polyvinyl chloride film,cross-linked polyethylene film has stronger charge accumulation ability and slower charge dissipation rate,which can better restrain the corona discharge of HVDC transmission lines.

Structural,Morphological and Electrical Properties of In-Doped Zinc Oxide Nanostructure Thin Films Grown on p-Type Gallium Nitride by Simultaneous Radio-Frequency Direct-Current Magnetron Co-Sputtering

Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.

Experimental Study on Ammonia Co-Firing with Coal for Carbon Reduction in the Boiler of a 300-MW Coal-Fired Power Station

To reduce CO_(2) emissions from coal-fired power plants,the development of low-carbon or carbon-free fuel combustion technologies has become urgent.As a new zero-carbon fuel,ammonia(NH_(3))can be used to address the storage and transportation issues of hydrogen energy.Since it is not feasible to completely replace coal with ammonia in the short term,the development of ammonia-coal co-combustion technology at the current stage is a fast and feasible approach to reduce CO_(2) emissions from coal-fired power plants.This study focuses on modifying the boiler and installing two layers of eight pure-ammonia burners in a 300-MW coal-fired power plant to achieve ammonia-coal co-combustion at proportions ranging from 20%to 10%(by heat ratio)at loads of 180-to 300-MW,respectively.The results show that,during ammonia-coal co-combustion in a 300-MW coal-fired power plant,there was a more significant change in NO_(x) emissions at the furnace outlet compared with that under pure-coal combustion as the boiler oxygen levels varied.Moreover,ammonia burners located in the middle part of the main combustion zone exhibited a better high-temperature reduction performance than those located in the upper part of the main combustion zone.Under all ammonia co-combustion conditions,the NH_(3) concentration at the furnace outlet remained below 1 parts per million(ppm).Compared with that under pure-coal conditions,the thermal efficiency of the boiler slightly decreased(by 0.12%-0.38%)under different loads when ammonia co-combustion reached 15 t·h^(-1).Ammonia co-combustion in coal-fired power plants is a potentially feasible technology route for carbon reduction.

Numerical Simulation of Combustion in 660MWTangentially Fired Pulverized Coal Boiler on Ultra-Low Load Operation

In this paper,the combustion conditions in the boiler furnace of a 660 MWtangential fired pulverized coal boiler are numerically simulated at 15%and 20%rated loads,to study the flexibility of coal-fired power units on ultra-low load operation.The numerical results show that the boiler can operate safely at 15%and 20%ultra-low loads,and the combustion condition in the furnace is better at 20%load,and the tangent circles formed by each characteristic section in the furnace are better,and when the boiler load is decreased to 15%,the tangent circles in the furnace begin to deteriorate.The average flue gas temperature of different areas of the furnace shows that when the boiler furnace operates under ultra-low load conditions,the average smoke temperature of the cold ash hopper at 20%load is basically the same as the average smoke temperature at 15%load;in the burner area,the average smoke temperature of the cold ash hopper at 20%load is about 50 K higher than that at 15%load;in the burned out area,the average smoke temperature of the cold ash hopper at 20%load is slightly higher than that at 15%load.The average temperature of flue gas in the furnace showed a tendency to increase rapidly with the height of the furnace,then slow down and fluctuate the temperature in the burner area,and finally increase slightly in the burnout area due to the further combustion of combustible components to release heat,and then began to decrease.

Optimizing Two-Phase Flow Heat Transfer:DCS Hybrid Modeling and Automation in Coal-Fired Power Plant Boilers

In response to escalating challenges in energy conservation and emission reduction,this study delves into the complexities of heat transfer in two-phase flows and adjustments to combustion processes within coal-fired boilers.Utilizing a fusion of hybrid modeling and automation technologies,we develop soft measurement models for key combustion parameters,such as the net calorific value of coal,flue gas oxygen content,and fly ash carbon content,within theDistributedControl System(DCS).Validated with performance test data,thesemodels exhibit controlled root mean square error(RMSE)and maximum absolute error(MAXE)values,both within the range of 0.203.Integrated into their respective automatic control systems,thesemodels optimize two-phase flow heat transfer,finetune combustion conditions,and mitigate incomplete combustion.Furthermore,this paper conducts an in-depth exploration of the generationmechanismof nitrogen oxides(NOx)and low oxygen emission reduction technology in coal-fired boilers,demonstrating a substantial reduction in furnace exit NOx generation by 30%to 40%and the power supply coal consumption decreased by 1.62 g/(kW h).The research outcomes highlight the model’s rapid responsiveness,enabling prompt reflection of transient variations in various economic indicator parameters.This provides a more effective means for real-time monitoring of crucial variables in coal-fired boilers and facilitates timely combustion adjustments,underscoring notable achievements in boiler combustion.The research not only provides valuable and practical insights into the intricacies of two-phase flow heat transfer and heat exchange but also establishes a pioneering methodology for tackling industry challenges.

Numerical Calculations and Cold Tests for Flow Fields of a 220t/h Retrofitted Oil-Boiler

In this paper, cold simulation experiments and numerical calculations are conducted to predict 3 D flow field aerodynamics for an oil furnace after being retrofitted due to its fuel variation. K ε model and SIMPLE program under body fit coordination (BFC) system, in which TTM non orthogonal method is used to control the irregular geometric boundary, are adopted to solve the control equations. Model tests are conducted to check the calculation results, showing that they are in agreement with each other. Three different alternatives with different side window locations are also calculated to optimize the designs. The field retrofitting results show that the combination of cold tests with numerical calculations has prosperous application in retrofitting or renewing medium and small boilers.

Three-Dimensional Dynamic Modeling of a Tangentially Fired Utility Boiler Furnace

The tangentially fired utility boiler furnace is divided into several sections. The dynamic mathematical models for each section are presented. In the combustion zone, three dimensional model is used, while for the upper sections, lumped parameter model is used instead. With the combination of different models, we can get detailed distributions of gas velocity, temperature, chemical species, heat flux, etc. in the furnace, but with less CPU time. The radiation through the interfaces of each section is cons...

Modeling and Simulation Study on Reverse Swirl of Secondary Air in Large Tangentially Fired Boiler

Based on the porosity method and the improved non uniform QUICK scheme, this paper describes a three dimensional computer simulation to predict the flow characteristics in a tangentially fired boiler. The model is applied to a 600?MW boiler modeling under different operating conditions of reverse swirl of secondary air. The numerical results achieve reasonable agreement with experimental data. The calculated results of flow field, the pressure distribution, the relative diameter of tangential circle, angular momentum flux in furnace and the velocity distribution index in horizontal gas pass are analyzed in detail. And then the effects of the reverse swirl of secondary air on flue gas imbalance are discussed. Finally a reasonable operating condition of the reverse swirl of secondary air is presented.

Neural network approach to predicting mercury emission from utility boiler

The feasibility of using an ANN method to predict the mercury emission and speciation in the flue gas of a power station under un-tested combustion/operational conditions is evaluated. Based on existing field testing datasets for the emissions of three utility boilers, a 3-layer back-propagation network is applied to predict the mercury speciation at the stack. The whole prediction procedure includes： collection of data, structuring an artificial neural network （ANN） model, training process and error evaluation. A total of 59 parameters of coal and ash analyses and power plant operating conditions are treated as input variables, and the actual mercury emissions and their speciation data are used to supervise the training process and verify the performance of prediction modeling. The precision of model prediction （ root- mean-square error is 0. 8 μg/Nm3 for elemental mercury and 0. 9 μg/Nm3 for total mercury） is acceptable since the spikes of semi- mercury continuous emission monitor （SCEM） with wet conversion modules are taken into consideration.

Analysis of Prese nt Operating Situati on of Large Size Coal-F ired Utility Boilers

Large size utility boilers develop rapidly in China, both their reliability and economics have reached better level. The operating situations of various existing boilers on the basis of different coals are analyzed, it is held that, the notable energy imbalance of furnace exit, ever existing in the tangential firing boilers has been solved, with comparatively lower NOX emission concentration of gained. The higher NOX emission concentration and furnace slagging etc. problems existing in wall firing boilers are notable. The comprehensive analysis shows that, it is appropriate to choose lower furnace volume heat release rate and higher flame height in the type selection design of boilers, and sufficient margin should be kept in the selection of coal pulverizing mills.

Characteristics of Phosphorus Adsorption with Boiler Slag and Process Optimization

[Objective] This study aimed to investigate the characteristics of phosphorus adsorption on boiler slag and optimize the adsorption process. [Method] Boiler slag was used as an adsorbent in the single-grade adsorption process to dispose the rural domestic sewage. During the course, phosphorus adsorption kinetics and thermodynamics, adsorption operating curve and the minimum boiler slag dosage were analyzed and calculated. [Result] Langmuir adsorption isotherm could be applied to describe the absorption of phosphorus with boiler slag, and the absorption kinetics was confirmed with the pseudo second-order equation. The maximum absorption quantity and the initial absorption rate increased with the rise of temperature, reaching up to 0.159 1 mg/g and 0.169 8 mg/(g·min) respectively at 40 ℃. Thermodynamic variables ΔG0<0 and ΔH0>0 indicated that the entire process was a spontaneous endothermic reaction, and high temperature would facilitate the reaction of absorption. In the single grade adsorption, the minimum adsorbent dosage decreased as the temperature rose; at 40 ℃ the optimum mass ratio of boiler slag to wastewater was 3.31 kg/m3. [Conclusion] The adsorption process with boiler slag as adsorbent is an economical and effective approach for treating rural domestic sewage.

INTRODUCTION TO INCONEL ALLOY 740: AN ALLOY DESIGNED FOR SUPERHEATER TUBING IN COAL-FIRED ULTRA SUPERCRITICAL BOILERS

Chinese utilities as well as those worldwide are facing increased demand for additional electricity, reduced plant emissions and greater efficiency. To meet this challenge will require increasing boiler temperature, pressure and coal ash corrosion resistance of the materials of boiler construction of future coal-fired boilers. A new nickel-based tube alloy, INCONEL^R alloy 740, is described aiming at meeting this challenge. Emphasis will be on describing the alloy＇ s mechanical properties, coal-ash and steam corrosion resistance. Microstructural stability as a function of temperature and time is addressed as well as some of the early methodology em- ployed to arrive at the current chemical composition.

Corrosion Behavior of TP316L of Superheater in Biomass Boiler with Simulated Atmosphere and Deposit

Corrosion behavior of TP316L was investigated with simulated atmosphere and ash deposition for the superheater in biomass boiler.Corrosion dynamic curves were plotted by mass gain.The results showed that the corrosion was dependent on temperature and was greatly accelerated by ash deposition.The mass gain was distinctly reduced in the presence of SO2 with and without ash deposition on the specimens.Corrosion rates with ash deposit at different temperatures were calculated.Two feasible methods were provided to avoid serious high-temperature corrosion in the biomass boiler.

Flexibility of a 300 MW Arch Firing Boiler Burning Low Quality Coals

Experimental investigations on the flexibility of a 300 MW Arch Firing (AF) coal-fired boiler when burning low quality coals is reported. Measurements of gas temperature and species concentration and char sampling using a water-cooled suction pyrometer were carried out along the furnace elevation. The carbon content and the size distribu-tions of the char samples were obtained. The char morphology was examined using a field emission scanning electron microscope (FESEM). The char sampling was performed on this type of boiler for the first time. The results indicate that the flexibility of this boiler burning low quality coals under a moderate boiler load is better than its flexibility under a high boiler load. Because of the insufficient capacity of the coal pulverizers used,in case of low coal quality the pul-verized coal fineness will drastically decrease under high boiler loads. This causes an increase in the loss due to incom-plete mechanical and chemical combustion. This is the main cause of a low burnout degree of the pulverized coal and the decrease of the flexibility of this AF boiler under a high boiler load.

Feasibility Analysis on the Integrated Application of Solar Energy, Biogas, Coal-fired Boiler and Radiant Floor Heating for Rural Residence

The feasibility of adopting a balanced energy mix mode (domestic solar energy, biogas, coal-fired boiler and radiant floor heating) was proposed. Taking a typical rural residence in Zhengzhou City for example, the study through theoretical analysis and calculation showed that such a balanced energy mix is an economic way and efficient in saving energy and reducing air pollution, and elaborated the theoretical feasibility of popularizing such a heat supply mode in rural areas.