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Records with Subject: Process Design
Showing records 443 to 467 of 2098. [First] Page: 1 15 16 17 18 19 20 21 22 23 Last
A New Method for Impeller Inlet Design of Supercritical CO2 Centrifugal Compressors in Brayton Cycles
Xiaojian Li, Yijia Zhao, Huadong Yao, Ming Zhao, Zhengxian Liu
April 3, 2023 (v1)
Keywords: centrifugal compressor, condensation, impeller inlet design, maximum swallowing capacity, supercritical carbon dioxide
Supercritical Carbon Dioxide (SCO2) is considered as a potential working fluid in next generation power and energy systems. The SCO2 Brayton cycle is advantaged with higher cycle efficiency, smaller compression work, and more compact layout, as compared with traditional cycles. When the inlet total condition of the compressor approaches the critical point of the working fluid, the cycle efficiency is further enhanced. However, the flow acceleration near the impeller inducer causes the fluid to enter two-phase region, which may lead to additional aerodynamic losses and flow instability. In this study, a new impeller inlet design method is proposed to achieve a better balance among the cycle efficiency, compressor compactness, and inducer condensation. This approach couples a concept of the maximum swallowing capacity of real gas and a new principle for condensation design. Firstly, the mass flow function of real gas centrifugal compressors is analytically expressed by non-dimensional pa... [more]
Experimental Investigation on Influence of Shed Parameters on Surface Rainwater Characteristics of Large-Diameter Composite Post Insulators under Rain Conditions
Yanpeng Hao, Yifan Liao, Zhiqiang Kuang, Yijie Sun, Gaofeng Shang, Weixun Zhang, Guiyun Mao, Lin Yang, Fuzeng Zhang, Licheng Li
April 3, 2023 (v1)
Keywords: composite post insulators, heavy rainfall, large-diameter, shed parameters, surface rainwater characteristics
The discharges of water columns and droplets between the sheds make the leakage distance not effectively used, which is one of the main reasons for flashover of composite post insulators under heavy rainfall. To study the influence of shed parameters on surface rainwater characteristics, artificial rain tests were carried out on the large-diameter composite post insulators under the rainfall intensity of 2−15 mm/min. Lwc (the length of water columns at the edge of large sheds), Nwc (the number of water columns at the edge of large sheds), Nwde (the number of water droplets at the edge of large sheds) and Nwds (the number of water droplets in the space between two adjacent large sheds) were proposed as the parameters of surface rainwater characteristics. The influences of large shed spacing, large shed overhang and rod diameter on the parameters of surface rainwater characteristics under different rainfall intensities were analyzed. The experimental results show that, under the same rai... [more]
Seasonal Energy Storage Potential Assessment of WWTPs with Power-to-Methane Technology
Zoltán Csedő, Botond Sinóros-Szabó, Máté Zavarkó
April 3, 2023 (v1)
Keywords: power-to-methane, seasonal energy storage, techno-economic assessment, wastewater treatment plants
Power-to-methane technology (P2M) deployment at wastewater treatment plants (WWTPs) for seasonal energy storage might land on the agenda of decision-makers across EU countries, since large WWTPs produce a notable volume of biogas that could be injected into the natural gas grid with remarkable storage capacities. Because of the recent rapid increase of local photovoltaics (PV), it is essential to explore the role of WWTPs in energy storage and the conditions under which this potential can be realized. This study integrates a techno-economic assessment of P2M technology with commercial/investment attractiveness of seasonal energy storage at large WWTPs. Findings show that a standardized 1 MWel P2M technology would fit with most potential sites. This is in line with the current technology readiness level of P2M, but increasing electricity prices and limited financial resources of WWTPs would decrease the commercial attractiveness of P2M technology deployment. Based on a Hungarian case st... [more]
Rational Design and Testing of Anti-Knock Additives
Andrew D. Ure, Manik K. Ghosh, Maria Rappo, Roland Dauphin, Stephen Dooley
April 3, 2023 (v1)
Keywords: anti-knock, fuel additives, ignition quality tester, phenol
An innovative and informed methodology for the rational design and testing of anti-knock additives is reported. Interaction of the additives with OH● and HO2● is identified as the key reaction pathway by which non-metallic anti-knock additives are proposed to operate. Based on this mechanism, a set of generic design criteria for anti-knock additives is outlined. It is suggested that these additives should contain a weak X-H bond and form stable radical species after hydrogen atom abstraction. A set of molecular structural, thermodynamic, and kinetic quantities that pertain to the propensity of the additive to inhibit knock by this mechanism are identified and determined for a set of 12 phenolic model compounds. The series of structural analogues was carefully selected such that the physical thermodynamic and kinetic quantities could be systematically varied. The efficacy of these molecules as anti-knock additives was demonstrated through the determination of the research octane number... [more]
Techno-Economic Assessment: Food Emulsion Waste Management
George Lazaroiu, Katarina Valaskova, Elvira Nica, Pavol Durana, Pavol Kral, Petr Bartoš, Anna Maroušková
April 3, 2023 (v1)
Keywords: bioeconomy, emulsion breakdown, process management, techno-economic assessment
Production of food-grade emulsions is continuously rising globally, especially in developing countries. The steepest demand growth is in the segment of inexpensive meat products where edible emulsions serve as lubricants to mitigate economic loses linked with mechanical damage during automated processing of artificial casings. Provided that production goal is to minimize emulsion transfer into the product, its vast majority becomes voluminous greasy and sticky waste. Public sewage treatment plants cannot process such waste, its cleaning processes tends to collapse under loads of emulsions. To make matters worse, composition of emulsions often changes (according to actual pricing of main components) and emulsion manufacturers carefully guard their recipes. Therefore, running of in-house sewage plants would require continuous experimentation linked with need for skilled personnel, frequent changes in technology setup and high operating costs in general. Consequently, it was repeatedly an... [more]
Tesla Bladed Pump (Disc Bladed Pump) Preliminary Experimental Performance Analysis
Yaguang Heng, Yuming Han, Huiyu Zhang, Weibin Zhang, Gérard Bois, Qifeng Jiang, Zhengwei Wang, Xiaobing Liu
April 3, 2023 (v1)
Keywords: centrifugal, experimental analysis, multiphase flow, performance characteristics, tesla bladed pump
A preliminary experimental work on a centrifugal pump model specifically designed to transport slurry and multiphase flows is presented. The impeller design corresponds to the so-called “Tesla Bladed Pump” adapted from an existing DiscflowTM pump design for the petroleum deep-sea application. The overall performance results of such a specific pump design are presented for different rotational speeds and discussed in relation to affinity laws coefficients. The results show that the performance of the tested disc pump strongly differs from the conventional centrifugal bladed pump. A one-dimensional approach using complete Euler relation is used to explain the differences in the present case. Moreover, it has been found that available results in open literatures do not correspond to the real optimum conditions, more detailed research work must be performed to get a better understanding on this kind of bladed disc pump.
Comparing Hydrogen Sulfide Removal Efficiency in a Field-Scale Digester Using Microaeration and Iron Filters
Joanna K. Huertas, Lawrence Quipuzco, Amro Hassanein, Stephanie Lansing
April 3, 2023 (v1)
Keywords: anaerobic digestion, biogas, desulfurization, H2S, sulfur-oxidizing bacteria
Biological desulfurization of biogas from a field-scale anaerobic digester in Peru was tested using air injection (microaeration) in separate duplicate vessels and chemical desulfurization using duplicate iron filters to compare hydrogen sulfide (H2S) reduction, feasibility, and cost. Microaeration was tested after biogas retention times of 2 and 4 h after a single injection of ambient air at 2 L/min. The microaeration vessels contained digester sludge to seed sulfur-oxidizing bacteria and facilitate H2S removal. The average H2S removal efficiency using iron filters was 32.91%, with a maximum of 70.21%. The average H2S removal efficiency by iron filters was significantly lower than microaeration after 2 and 4 h retention times (91.5% and 99.8%, respectively). The longer retention time (4 h) resulted in a higher average removal efficiency (99.8%) compared to 2 h (91.5%). The sulfur concentration in the microaeration treatment vessel was 493% higher after 50 days of treatments, indicatin... [more]
Comparative Analysis and Design of a Solar-Based Parabolic Trough−ORC Cogeneration Plant for a Commercial Center
Eduardo A. Pina, Luis M. Serra, Miguel A. Lozano, Adrián Hernández, Ana Lázaro
April 3, 2023 (v1)
Keywords: Biomass, commercial center, CSP, parabolic trough, solar cogeneration, solar cooling
This paper performs technical, economic and environmental feasibility analyses of two different solar cogeneration plants, consisting of a solar system (a parabolic trough collector field coupled with thermal energy storage), an Organic Rankine Cycle (ORC), and mechanical chillers, that should cover the electrical and cooling demands of a commercial center located in Zaragoza (Spain). System A is hybridized with an auxiliary biomass boiler that complements the solar system’s thermal production, providing a constant heat supply to the ORC, which operates at full load during the operating hours of the solar system. In contrast, system B is not hybridized with biomass, so the ORC is fully driven by the solar system, operating at partial load according to the solar resource availability. Both systems are connected to the electrical grid, allowing electricity purchases and sales when needed. The design procedure involves the sizing of the equipment as well as the modelling of the hourly beh... [more]
A Comparison of Dispatchable RES Technoeconomics: Is There a Niche for Concentrated Solar Power?
Alexandra G. Papadopoulou, George Vasileiou, Alexandros Flamos
April 3, 2023 (v1)
Keywords: concentrated solar power, Energy Storage, levelized cost of electricity, net present value, offshore wind, photovoltaics, renewable energy sources, sensitivity analysis, techno-economic assessment, wind energy
Raising the penetration of renewable energy sources constitutes one of the main pillars of contemporary decarbonization strategies. Within this context, further progress is required towards the optimal exploitation of their potential, especially in terms of dispatchability, where the role of storage is considered vital. Although current literature delves into either storage per se or the integration of storage solutions in single renewable technologies, the comparative advantages of each technology remain underexplored. However, high-penetration solutions of renewable energy sources (RES) are expected to combine different technological options. Therefore, the conditions under which each technology outperforms their counterparts need to be thoroughly investigated, especially in cases where storage components are included. This paper aims to deal with this gap, by means of assessing the combination of three competing technologies, namely concentrated solar power (CSP), photovoltaics (PV)... [more]
Experimental Design, Instrumentation, and Testing of a Laboratory-Scale Test Rig for Torsional Vibrations—The Next Generation
Aditya Sharma, Saket Srivastava, Catalin Teodoriu
April 3, 2023 (v1)
Keywords: drilling automation, drilling technology, drilling vibrations, Machine Learning, stick-slip
Drilling technology and specially drilling equipment has dramatically changed in the last 10 years through intensive and innovative technologies, both in terms of hardware and software. While engineers are focusing on safer, faster, and more reliable than ever technologies, big data and automation are currently considered the way forward to achieve these goals. Especially when automation concepts are proposed, the prior testing and qualification under a laboratory-controlled environment are mandatory. Drilling simulators have been hugely successful in training industry personnel and academic professionals. A big reason for its success lies in the seamless integration of hardware and software to include an interactive user interface. Physical experimental simulators have the advantage of exposing the user with visual and auditive aids to better understand the real process. This paper provides an insight into the construction and results obtained using a dedicated laboratory setup, which... [more]
Evaluation of Daylight and Cooling Performance of Shading Devices in Residential Buildings in South Korea
Taesub Lim, Woong Seog Yim, Daeung Danny Kim
April 3, 2023 (v1)
Keywords: cooling energy, daylight, residential building, shading device
Accounting for more than half of buildings in South Korea, the energy consumed by residential buildings has become a main concern and the cooing demand has rapidly increased. To reduce energy consumption, several passive and active design strategies have generally been applied. However, there has been an increasing demand for high window-to-wall ratios in residential buildings, it is imperative to block sunlight into a building effectively. Focusing on the reduction of cooling energy consumption in a residential building, the present study assessed the daylight and energy performance of shading devices. Among various types of shading devices, the Venetian blind, horizontal louver, light shelf, and egg-crate were selected. The illuminance levels in three different areas in a building were measured. In addition, the annual cooling energy consumption by these shading devices was investigated. As a result, both daylight and energy performance varied with different design options of these s... [more]
Dynamic Modelling and Techno-Economic Assessment of a Compressed Heat Energy Storage System: Application in a 26-MW Wind Farm in Spain
Violeta Sánchez-Canales, Jorge Payá, José M. Corberán, Abdelrahman H. Hassan
April 3, 2023 (v1)
Keywords: high-temperature heat pump, organic Rankine cycle, thermal energy storage, transient modelling
One of the main challenges for a further integration of renewable energy sources in the electricity grid is the development of large-scale energy storage systems to overcome their intermittency. This paper presents the concept named CHEST (Compressed Heat Energy STorage), in which the excess electricity is employed to increase the temperature of a heat source by means of a high-temperature heat pump. This heat is stored in a combination of latent and sensible heat storage systems. Later, the stored heat is used to drive an organic Rankine cycle, and hereby to produce electricity when needed. A novel application of this storage system is presented by exploring its potential integration in the Spanish technical constraints electricity market. A detailed dynamic model of the proposed CHEST system was developed and applied to a case study of a 26-MW wind power plant in Spain. Different capacities of the storage system were assessed for the case under study. The results show that roundtrip... [more]
Use of AMT Transformers and Distributed Storage Systems to Enhance Electrical Feeding Systems for Tramways
Romano Giglioli, Giovanni Lutzemberger, Luca Sani
April 3, 2023 (v1)
Keywords: amorphous transformer, Energy Storage, failure, feeding substation, tramway
Tramway systems are more and more diffused today, to reduce pollution and greenhouse emissions. However, their electrical feeding substations can have significant margin for improvement. Therefore, it is questionable which kind of changes can be introduced, by changing their main features. First of all, transformer technology can be enhanced, by moving from the standard transformer to the amorphous metal one; thus, guaranteeing a significant reduction in losses. Then, by installing one dedicated storage systems for each substation. This solution can help to increase the energy efficiency; thus, recovering the tram braking energy and reducing the delivered energy from the grid, and also the reliability of the system; thus, guarantee different levels of services, in the case of failure of a feeding substation. This paper investigates in a systematic approach the two proposed solutions. In particular an amorphous metal transformer has been properly designed, and performance compared to th... [more]
Heterogeneity of Electricity Consumption Patterns in Vulnerable Households
Gianluca Trotta, Kirsten Gram-Hanssen, Pernille Lykke Jørgensen
April 3, 2023 (v1)
Keywords: cluster analysis, Denmark, domestic electricity consumption patterns, heterogeneity, time-varying rates, vulnerable households
A key aspect of the design of specific tariff structures is to identify and characterize homogeneous electricity consumption profiles. Recent research in residential electricity demand has explored load profile segmentation via cluster analysis combined with descriptive data from the dwelling and occupants, which has partly explained electricity load patterns and their underlying drivers but has failed to investigate any consumption heterogeneity among similar households. Thus, the aim of this paper is to reverse this approach and investigate the extent that households with similar characteristics have different electricity consumption patterns. This study combines population-based register data with hourly electricity consumption data for a sample of 67 Danish households. First, a homogenous household group is selected based on several indicators that signal vulnerability. The specific group under investigation is single-person, older, low-income households in detached housing. Second... [more]
Impact of First Tower Earthing Resistance on Fast Front Back-Flashover in a 66 kV Transmission System
Abdullah H. Moselhy, Abdelaziz M. Abdel-Aziz, Mahmoud Gilany, Ahmed Emam
April 3, 2023 (v1)
Keywords: back-flashover, fast front transient study, footing resistance, insulation coordination, lightning impulse withstand voltage, PSCAD/EMTDC
Lightning stroke on a transmission tower structure is one of the major reasons that results in high voltages at the tower arms due to the excessive lightning current flowing through the transmission tower to earth. The Surge voltage seen at the tower cross arm on the first tower close to a substation is the worst case. If this voltage is higher than the withstand level of the insulator string, the insulation of substation equipment will be exposed to transient over-voltage called fast front back-flashover (FFBF). The peak of this transient overvoltage is affected by the value of the system’s earthing resistance. This paper studies the effect of reducing the grounding resistance of both the surge arrestor (SA) and the first transmission line tower adjacent to a 66 kV substation on FFBF. Three case studies using PSCAD/EMTDC software are presented to simulate the variation of the potential sire at the substation equipment with different resistance values for the first tower and SA earthin... [more]
An Experimental Study on the Fire Spread Rate and Separation Distance between Facing Stores in Passage-Type Traditional Markets
Hong-Seok Yun, Dong-Gun Nam, Cheol-Hong Hwang
March 31, 2023 (v1)
Keywords: fire spread rate, maximum heat release rate, radiant heat flux, separation distance, traditional market
Real-scale fire experiments were conducted to understand the fire spread characteristics of the major combustibles handled in traditional markets, a space with high fire risk. The major combustibles were selected through field surveys administered at a number of traditional markets. Through real-scale fire experiments, the horizontal fire spread rate according to the maximum heat release rate of major combustibles was examined. In addition, the separation distance to prevent fire spread to the facing store by radiant heat transfer was examined. As a result of the experiments, it was confirmed that the arrangement method of the combustibles causes a large change in the maximum heat release rate, fire growth rate, and fire spread rate. The horizontal fire spread rate showed a linear proportional relationship with respect to the maximum heat release rate regardless of the type of combustibles, and a correlation to define the relationship was proposed. A correlation equation for predicting... [more]
Analysis of Standby Losses and Charging Cycles in Flywheel Energy Storage Systems
Mustafa E. Amiryar, Keith R. Pullen
March 31, 2023 (v1)
Keywords: aerodynamic windage loss, bearing friction loss, flywheel energy storage, flywheel standby loss, windage drag coefficient
Aerodynamic drag and bearing friction are the main sources of standby losses in the flywheel rotor part of a flywheel energy storage system (FESS). Although these losses are typically small in a well-designed system, the energy losses can become significant due to the continuous operation of the flywheel over time. For aerodynamic drag, commonly known as windage, there is scarcity of information available for loss estimation since most of the publications do not cover the partial vacuum conditions as required in the design of low loss energy storage flywheels. These conditions cause the flow regime to fall between continuum and molecular flow. Bearings may be of mechanical or magnetic type and in this paper the former is considered, typically hybridized with a passive magnetic thrust bearing. Mechanical bearing loss calculations have been extensively addressed in the open literature, including technical information from manufacturers but this has not previously been presented clearly a... [more]
Design, Development, and Performance of a 10 kW Polymer Exchange Membrane Fuel Cell Stack as Part of a Hybrid Power Source Designed to Supply a Motor Glider
Magdalena Dudek, Andrzej Raźniak, Maciej Rosół, Tomasz Siwek, Piotr Dudek
March 31, 2023 (v1)
Keywords: aviation, Hydrogen, motor glider, polymer exchange membrane fuel cell stack, propulsion system
A 10 kW PEMFC (polymer exchange membrane fuel cell) stack consisting of two 5 kW modules, (A) and (B), connected in series with a multi-function controller unit was constructed and tested. The electrical performance of the V-shaped PEMFC stack was investigated under constant and variable electrical load. It was found that the PEMFC stack was capable of supplying the required 10 kW of electrical power. An optimised purification process via ‘purge’ or humidification, implemented by means of a short-circuit unit (SCU) control strategy, enabled slightly improved performance. Online monitoring of the utilisation of the hydrogen system was developed and tested during the operation of the stack, especially under variable electrical load. The air-cooling subsystem consisting of a common channel connecting two 5 kW PEMFC modules and two cascade axial fans was designed, manufactured using 3D printing technology, and tested with respect to the electrical performance of the device. The dependence... [more]
Formation Kinetics of the Mixed Cyclopentane—Carbon Dioxide Hydrates in Aqueous Sodium Chloride Solutions
Xuebing Zhou, Ye Zhang, Xiaoya Zang, Deqing Liang
March 31, 2023 (v1)
Keywords: Carbon Dioxide, cyclopentane, desalination, gas hydrate, PXRD
Hydrate formation from cyclopentane (CP) and carbon dioxide was measured at 281 K by powder X-ray diffraction (PXRD) and macroscopic methods. The effect of initial pressure and CP mass fraction in liquid phase was analyzed. The results showed that hydrate formation was assumed to start with the nucleation of the mixed CP-CO2 hydrate with small fraction of CO2 followed by a large continuous CO2 adsorption. Initial pressure was found to have a positive correlation with the total CO2 consumptions when the initial pressure was below 2.5 MPa. However, the total CO2 consumptions dropped by over a half as the initial pressure was 3.0 MPa. PXRD revealed that all the hydrate samples formed at different initial pressures were structure II. The CO2 consumptions were assumed to be inhibited by the competitive occupation of 51264 cages between CP and CO2 molecules when the initial pressure was above 2.5 MPa. The CO2 consumptions were also found to be reduced as the CP mass fraction was above 0.25.... [more]
Liquid-Liquid Flow Pattern Prediction Using Relevant Dimensionless Parameter Groups
Olusegun Samson Osundare, Gioia Falcone, Liyun Lao, Alexander Elliott
March 31, 2023 (v1)
Keywords: dimensionless numbers, flow regime, geo-energy, oil-viscosity, oil-water, pipe diameter
Accurate predictions of flow patterns in liquid-liquid flow are critical to the successful design and operation of industrial and geo-energy systems where two liquids are jointly transported. Unfortunately, there is no unified flow pattern map, because all published maps are based on limited ranges of dimensional parameters. Dimensional analysis was performed on oil-water horizontal flows, to obtain some relevant dimensionless parameter groups (DPG) for constructing flow pattern maps (FPM). The following combinations of DPG were used: (i) the ratio of mixture Reynolds number to Eötvös number versus water fraction, (ii) the ratio of Weber number to Eötvös number versus water fraction, (iii) the mixture Froude number versus water fraction, (iv) the water Froude number versus oil Froude number, (v) the ratio of gravity force to viscous force versus water fraction. From twelve published experimental studies, 2696 data points were gathered and analysed covering a variety of flow patterns in... [more]
Optimal Design of Multi-Output LLC Resonant Converter with Independently Regulated Synchronous Single-Switched Power-Regulator
Sang Gab Park, Byoung Kuk Lee, Jong Soo Kim
March 31, 2023 (v1)
Keywords: 3D, inductor-inductor-capacitor (LLC), LED driver, multi-output, resonant converter, soft switching, SSPR, zero voltage switching (ZVS)
This paper presents a tightly regulated multi-output isolated converter that employs only an independently regulated synchronous Single-Switched Post-Regulator (SSPR). The proposed converter is a highly accurate single-ended secondary side post-regulator based on a Series Resonant Converter (SRC); furthermore, it has a voltage-doubler characteristic. The proposed post-regulator requires only one auxiliary switch, in contrast with a bulky and expensive non-isolated DC−DC converter. Moreover, the added voltage-doubler can tightly regulate the slave output current. In addition, the voltage-doubler can improve electromagnetic interference characteristics and reduce switching losses arising from the Zero Current Switching (ZCS) operation of all power switches. The validity of the proposed converter is verified using experimental results obtained via a prototype converter applicable to an LED 3D TV power supply.
Zero-Airgap Induction Motor Used to Drive a Transmission Oil Pump
Dan-Cristian Popa, Nicolae-Florin Jurca, Razvan Alexandru Inte, Nicholas Hrusch, Jeff Hemphill, Codrin G. Cantemir
March 31, 2023 (v1)
Keywords: induction motor, transmission oil pump, zero-airgap
In this paper, we propose a novel study concerning the future use of a zero-airgap induction motor in applications related to transmission oil pumps. The name of the machine comes from the fact that the rotor touches the stator as it spins. The use of such an eccentric motor provides the possibility to remove the mechanical part that is typically found in the transmission oil pump, increasing its efficiency in this way. We focused on determining the optimum variant of a zero-airgap small power induction motor from the point of view of the electrical and mechanical performance. As such, 18 topologies of induction motors with various numbers of pole pairs and rotor bars were designed and numerically analyzed. For the best variant from each category, different eccentricities were considered to evaluate this effect over the performances of the motors. For the best candidate, various analyses were performed in order to demonstrate the validity of this solution for the proposed application.... [more]
AC−DC Flyback Dimmable LED Driver with Low-Frequency Current Ripple Reduced and Power Dissipation in BJT Linearly Proportional to LED Current
Yeu-Torng Yau, Kuo-Ing Hwu, Kun-Jie Liu
March 31, 2023 (v1)
Keywords: bipolar junction transistor (BJT), current ripple, dimmable, light-emitting diode (LED), linear current regulator, output voltage automatic regulator, power factor (PF), single-stage AC–DC flyback converter, total harmonic distortion (THD)
In this paper, a dimmable light-emitting diode (LED) driver, along with the low-frequency current ripple decreased and the bipolar junction transistor (BJT) power dissipation reduced, is developed. This driver is designed based on a single-stage flyback converter. On the one hand, the low-frequency output current ripple reduction is based on the physical behavior of the linear current regulator. On the other hand, when the voltage across the LED string is decreased/increased due to dimming or temperature, the output voltage of the flyback converter will be automatically regulated down/up, thereby making the power dissipation in the BJT linearly proportional to the LED current. By doing so, not only the power loss in the linear current regulator will be decreased as the LED current is decreased or the LED temperature rises, but also the output current ripple can be reduced. Furthermore, the corresponding power factor (PF) is almost not changed, and the total harmonic distortion (THD) is... [more]
Development and Experimental Study of the First Stage in a Two-Stage Water-Flooded Single-Screw Compressor Unit for Polyethylene Terephthalate Bottle Blowing System
Ting Li, Yuchuan Wang, Xiuli Mao, Diyi Chen, Rui Huang, Quanke Feng
March 31, 2023 (v1)
Keywords: dehumidification, isentropic efficiency, polyethylene terephthalate bottle blowing system, pressure loss, water-flooded single-screw compressor
The oil-free compressor is a key component in fabricating polyethylene terephthalate (PET) bottles for beverages and water. At present, the main compressor type used for blowing PET bottles is the reciprocating compressor. However, compared to screw compressors, reciprocating compressors have shortcomings of high energy consumption and too many consumable parts. Many manufacturers of PET bottles in Asia are seeking to replace reciprocating compressors with screw compressors, as we know. Screw compressors can be classified as single-screw compressors (SSC) and twin-screw compressors. Since the load in a twin-screw compressor is far larger than that in an SSC, SSCs are more suitable for being developed for high-pressure applications such as PET bottle blowing. This paper presents a performance study on an oil-free single-screw compressor as the first stage of the PET compressor unit. A 5.4 m3·min−1 prototype and its test rig were developed. The thermophysical process of the moist air is... [more]
Understanding the Effect of Cementitious Grouting Pressure on Micro-Fracture Permeability for Rock Reinforcement Underground: A Lab Study
Kai Wang, Lianguo Wang, Bo Ren, Hao Fan
March 31, 2023 (v1)
Keywords: fracture opening, grouting pressure, micro-fracture, percolation effect, ultrafine cement (UFC)
In grouting support projects, due to the small concealment of micro-fractures, the support effect often fails to meet design requirements. The percolation effect is a common factor that causes grouting failure, and the influence of grouting pressure on the percolation effect is very obvious. In this article, a design of a micro-fracture grouting experimental system is presented that can realize high-pressure grouting and then uses a variety of ultrafine cements to carry out high- and low-pressure grouting tests under different fracture opening conditions, thereby obtaining the grouting pressure and accumulated grouting weight during the grouting process. The results show that a combination of the grouting pressure curve and the cumulative grouting weight curve can determine whether the ultrafine cement will have a percolation effect. Increasing the grouting pressure can reduce the critical fracture opening value and also reduce the occurrence of the percolation effect. The research res... [more]
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