Operational Performance Characteristics Research Articles

Operational Performance and Weld Bead Characteristics of Experimental Tubular-Wires for Underwater Welding

Operational Performance and Weld Bead Characteristics of Experimental Tubular-Wires for Underwater Welding

Review of Energy Storage Capacitor Technology

Capacitors exhibit exceptional power density, a vast operational temperature range, remarkable reliability, lightweight construction, and high efficiency, making them extensively utilized in the realm of energy storage. There exist two primary categories of energy storage capacitors: dielectric capacitors and supercapacitors. Dielectric capacitors encompass film capacitors, ceramic dielectric capacitors, and electrolytic capacitors, whereas supercapacitors can be further categorized into double-layer capacitors, pseudocapacitors, and hybrid capacitors. These capacitors exhibit diverse operational principles and performance characteristics, subsequently dictating their specific application scenarios. To make informed decisions in selecting capacitors for practical applications, a comprehensive knowledge of their structure and operational principles is imperative. Consequently, this review delved into the structure, working principles, and unique characteristics of the aforementioned capacitors, aiming to clarify the distinctions between dielectric capacitors, supercapacitors, and lithium-ion capacitors.

Basic performance, cavitation and runaway investigations of a high specific speed Francis turbine with emphasis on cavitation analysis: A case study

The paper presents comprehensive experimental research on a high specific speed model Francis turbine with a characteristic runner diameter of 250 mm under the head of 12 m. Essentially, the turbine was designed for use at heads between 10 and 50 m, which are typical for installations with low specific speed Kaplan turbines. The basic performance, cavitation and runaway characteristics of the machine, which were determined as a result of the work, are quite rarely available in the literature in the case of high specific speed Francis turbines. The turbine achieved the maximum efficiency of 91%, kinematic specific speed of 82, and relatively wide operation range, so that it can be attractive as an alternative to the low specific speed Kaplan, semi-Kaplan or propeller turbines.In result of the basic laboratory tests, the performance characteristics of the machine operation in a wide range of guide vane opening angles between 9° and 36° as well as the shell efficiency characteristics were determined. On the characteristics plotted vs. rotational speed, the saddle effect was identified for the guide vane opening angles with values greater than the optimal one (22°). During the operation of the machine in the area of saddles, the change in the flow rate took quite surprising patterns. The share of the turbine thrust torque in the total torque was also determined, the characteristics of which are also burdened with a similar saddle effect.In the case of cavitation tests, a multi-aspect approach to cavitation diagnostics was used to characterize the cavitation phenomenon from the viewpoint of various criteria. Following this approach, the signals of the draft tube wall acceleration, acoustic emission at the draft tube cone upper flange, and pressure fluctuations inside the draft tube were used. The determined cavitation characteristics indicate little cavitation susceptibility of the Francis turbine blade system, despite the presented turbine having been designed to operate at higher flow rates than the classic high head Francis turbines with long interblade channels. The cavitating flow in the draft tube, directly below the runner, was also visualized during the cavitation tests. The paper presents the results of visualization for all cavitation states at five selected settings of the guide vane opening angle (two states in Partial Load, two states in High Load area and one state in the Best Efficiency Point), thanks to which it was possible to track the development of vortices during pressure reduction in the flow system.The runaway coefficient was determined as a result of the runaway tests. The value of 1.497 was reached at the optimum guide vane opening angle.Additionally, the work also presents in detail the efficiency scale effects to be expected at prototype turbines, i.e. those intended for operation at a higher head and with larger runner diameters. The efficiency of the machine with a runner diameter of 1.5 m and working at a head of 50 m reaches ∼93%. The influence of water viscosity on the change in efficiency of the prototype turbine is also shown.The presented methodology can be used for the proper selection of turbines intended for hydropower plants and for the proper installation of the runner in respect to the tailwater level in order to avoid the phenomenon of cavitation erosion.

Performance investigation and operation optimization of an innovative hybrid renewable energy integration system for commercial building complex and hydrogen vehicles

With the increasing in energy demands and carbon emissions of building and transport sectors, improving the penetration of renewable resources in these areas are inevitable trends. To further develop the theoretical method of energy integrated system in building/transportation area, load forecasting of commercial building complex and hydrogen vehicles are determined, a novel hybrid renewable energy integration system is presented and studied. Thermal, economic and environmental performances for poly-generation system are performed and optimized, optimal performance and configuration are obtained by NSGA-II algorithm and TOPSIS-Shannon entropy weight method. In addition, operating performance characteristics of integration system during typical weekday and weekend in different seasons are analyzed, the influences of critical parameters on comprehensive performances of integrated system are also conducted. The results showed that optimal exergetic efficiency, levelized cost of product (LCOP) and levelized CO2 emissions of product (LCEP) are 12.61 %, 0.0711 $/kWh and 0.0185 kg/kWh. Furthermore, thermodynamic performances of proposed system decreases while LCOP and LCEP rise with the increasing in HVs stock. Biomass and purchased electricity prices have different impacts on system comprehensive performances. In general, this study provides a new alternative for multiple renewable energy integrated system optimization in building and transportation sectors.

Reviewing Control Paradigms and Emerging Trends of Grid-Forming Inverters—A Comparative Study

Grid-forming inverters (GFMs) have emerged as crucial components in modern power systems, facilitating the integration of renewable energy sources and enhancing grid stability. The significance of GFMs lies in their ability to autonomously establish grid voltage and frequency, enabling grids to form and improve system flexibility. Discussing control methods for grid-forming inverters is paramount due to their crucial role in shaping grid dynamics and ensuring reliable power delivery. This paper explores the fundamental and advanced control methods employed by GFMs, explaining their operational principles and performance characteristics. Basic control methods typically involve droop control, voltage and frequency regulation, and power-balancing techniques to maintain grid stability under varying operating conditions. Advanced control strategies encompass predictive control, model predictive control (MPC), and adaptive control, which influence advanced algorithms and real-time data for enhanced system responsiveness and efficiency. A detailed analysis and performance comparison of different control methods for GFM is presented, highlighting their strengths, limitations, and suitability for diverse grid environments. Through comprehensive studies, this research interprets the ability of various control strategies to mitigate grid disturbances, optimize power flow, and enhance overall system stability.

Triple‐band circularly polarized conformal antenna for vehicular communication applications

AbstractVehicular communication presents a compact wideband implantable antenna for the best wireless transmission of information. The key role of the antenna is handled by the thickness of the substrate present in that antenna. Also, the shape of the antenna causes the performance characteristics. Now, vehicle‐to‐vehicle communication is the interesting task for designers to create successful and organized vehicular communication systems. This article presents a triple‐band circularly polarized conformal antenna for vehicular communication. An antenna is introduced as a triple‐band circular polarized conformal antenna and preserved a suitable mount on the vehicle surface for greater gain to provide well‐maintained operational performance characteristics. For getting circular polarization, circular cuttings are provided in the design of the proposed antenna. The radiation gives a fixed direction by providing 0.3 mm thickness. Here, use a circularly polarized antenna to rectify the signal absorption due to the contact material used in the antenna. A polyamide material is used as a substrate to get a probable successful link and improve the flexibility of the antenna. The triple‐band circularly polarized antenna is designed to operate in vehicular communication bands such as 2.4 GHz Wi‐Fi, 3.5 GHz WiMAX, and 5.9 GHz dedicated short range communication. The antenna is designed to resonate in a triple band to improve the antenna parameters like frequency response characteristics, gain, return loss, voltage standing wave ratio, left hand circularly polarization, right hand circularly polarization, axial ratio, fidelity factor, directivity, radiated power, and input impedance. Under the operating frequency bands of 2.4, 3.4, and 5.9 GHz, the efficiency of the proposed antenna is 98.48%, 97.31%, and 97.90%, respectively. The triple‐band circularly polarized conformal antenna is implemented in the high‐frequency structure simulator platform. The proposed tri‐band antenna is applicable in vehicular communication systems and healthcare for efficient wireless transmission.

Operating performance characteristics and analysis of a high temperature fuel cell system integrated with a methanol steam reformer

A high temperature proton exchange membrane fuel cell system integrated with a methanol steam reformer is developed in this study. A system model considering thermal-coupled balance-of-plant components and several temperature constraints is established. The hydrogen production performance of the reformer is evaluated and experimentally validated. A high methanol conversion rate above 90.1% with a low CO content below 1.5% are obtained with the reformer temperature of 573 K at a steam to carbon ratio of 1.3. Besides, CO poisoning effect on the stack is inhibited with an increase in the operating temperature. The fuel cell voltage increases 35% with variation of the operating temperature from 160 °C to 180 °C at the current density of 0.4 A/cm2 and CO molar ratio of 1%. Furthermore, model-based analysis is conducted to investigate impacts of various input parameters on system operating performance. The proposed system presents a maximum electrical efficiency of 37.8%, and increasing the current density and decreasing air excess ratio are favorable for improving the net power output, but also increasing the heat duties of components and resulting in a reduced safety operating region. Finally, an optimal operating strategy with maximum system efficiency is proposed for variable output powers ranging from 15 to 55 W.

Product recall and CEO compensation: Evidence from the automobile industry

This study examines the association between product recall and CEO compensation. Using a sample of U.S. automobile industry product recalls from 1999 to 2018, we find that product recalls have significant negative impacts on CEO compensation. Our findings hold after controlling for the common determinants of CEO compensation, such as firms’ stock market and operating performance and CEO-specific characteristics. An additional analysis shows that CEOs’ total and long-term compensation decreases with the number of recalls. However, we find no association between CEOs’ cash compensation and product recalls.

Experimental and numerical study on the performances of a free-piston engine generator using ammonia and methane fuel mixtures

In this paper, experimental and numerical studies of the methane-ammonia dual-fuel glow-ignition free-piston engine generator (FPEG) are carried out, with emphasis on its operation stability, performance and combustion characteristics. The ammonia in FPEG operates at different energy substitution rates (ESRs), including 100 %CH4, 90 %CH4+10 %NH3, 80 %CH4+20 %NH3, and 70 %CH4+30 %NH3. The experimental results show that the FPEG can achieve stable operation in the methane/ammonia dual-fuel combustion mode. However, the operation stability of the FPEG becomes worse with the increase of the ESR. Especially when ESR = 30 %, engine shutdown accident will occur due to the high cycle-to-cycle variation caused by ignition delay. The peak pressure and heat release rate (HRR) decrease significantly because the additive ammonia weakens the combustion activity and reduces the combustion rate of mixture. In the case of pure methane, the indicated power and indicated thermal efficiency reach 319 W and 11.33 %, respectively. However, when ESR = 10 %, 20 % and 30 %, the corresponding values decrease significantly to 210 W, 7.48 %, 189 W, 6.72 % and 139 W, 4.95 %, respectively. The high-speed flame images show that with the increase of ESR, the flame structure becomes less wrinkled, because the addition of ammonia reduces the flame speed and weakens the combustion reaction, leading to the weakening of turbulent combustion intensity. In addition, the ammonia addition will also lead to post combustion phenomenon. The simulation results show that the start of combustion (SOC) is delayed and the crank angle (CA) 0–10 and CA10-50 are prolonged with the increase of ESR, because the ammonia addition reduces the amount of key radical, such as OH and H, which reduces the mixture reaction rate. The NOx emission decreases with the increase of ESR due to the low combustion temperature. Soot emissions from the pure methane remain extremely low, and the CO emissions gradually increase with the increase of ESR due to the incomplete combustion of mixture. In addition, the amount of unburned ammonia increases with the increase of ESR.

P72: Fully Coupled Computational Simulation of the Syncardia Total Artificial Heart May Optimize Clinical Performance

Background: The Syncardia Total Artificial Heart (TAH) is used as a bridge to transplant for patients with biventricular heart failure and currently the only FDA approved TAH. There is a dearth in studies investigating its mechanics, hemodynamics, and optimal performance. Previous studies have provided limited characterization of Syncardia’s dynamics with respect to platelet activation but did not fully realize a complete dynamic coupled solution. Thus, there is a knowledge gap with regards to understanding the operational capacity and performance characteristics of the TAH. The objective of this study is to characterize the hemodynamic performance of the Syncardia TAH to optimize operational parameters and further understand why the device is an effective bridge to transplant. Methods: COMSOL Multiphysics (COMSOL Inc.) was used to conduct fully coupled fluid-structure interaction simulations of the device in standard operation. The computational model contained a blood fluid volume within Syncardia’s housing assembly (ventricle), segmented polyurethane solution (SPUS) diaphragm chamber filled with air, and SynHall valves in the mitral and aortic positions. These components’ coupled physics allow for the cohesive motion of the blood volume, diaphragm, and valves by solving the fluid Navier-Stokes and solid motion equations. Results: Figure 1C is flow patterning representative of the left ventricular diastolic filling with the development of the ventricular vortex present within diastole. Negative pressure collapses and deforms the diaphragm as shown in Figure 1D to drive filling during diastole. Figure 1E shows regional stress on the SynHall mitral valve during diastole. Conclusions: We utilized a fully coupled model of the Syncardia to study hemodynamic properties including vorticity and shear stress spatial and temporal distributions. Future work will be to perform failure mode analysis to identify parameters that are associated with thrombosis as well as optimize clinical operational parameters including device setting and associated clinical management.

Milestones, hotspots and trends in the development of electric machines

As one of the greatest inventions of human beings, the electric machine (EM) has realized the mutual conversion between electrical energy and mechanical energy, which has essentially led humanity into the age of electrification and greatly promoted the progress and development of human society. This paper will briefly review the development of EMs in the past two centuries, high-lighting the historical milestones and investigating the driving force behind it. With the innovation of theory, the progress of materials and the breakthrough of computer science and power electronic devices, the mainstream EM types has been continuously changing since its appearance. This paper will not only summarize the basic operation principle and performance characteristics of traditional EMs, but also that of the emerging types of EMs. Meanwhile, control and drive system, as a non-negligible part of EM system, will be complementarily introduced. Finally, due to the background of global emission reduction, industrial intelligentization and transportation electrification, EM industry will usher again in a golden period of development. Accordingly, several foreseeable future developing trends will be analyzed and summarized.

Operational performance characteristics of an axial double baffles three channels classifier for coarse pulverized coal

In order to obtain the working principle of the axial direction classifier and raise its separation efficiency, the flow field and classification performance of the classifier was investigated by numerical simulation and experimental measurement. The particle size distribution at inlet, outlet and return pipe was measured by laser particle size analyzer and coupled with Rosin-Rammler model. The particle trajectory was analyzed using the discrete phase model. The tangential velocities played a dominant role in particles radial distribution mainly in the form of Rankine vortex. The axial velocities determine the vertical distribution of particles. The velocity distributions and turbulence influence the cutting particle size and separation efficiency mostly. The most suitable condition is baffles angle of 20° and inlet velocity of 19.3 m/s considering the load of the mill and the fineness of the pulverized coal at the inlet of the classifier.

Investigation of Performance and Emission Characteristics of Diesel-Ethanol PCCI Engine

Using numerical analysis and the ANSYS Forte 19.2 package, this study investigates the performance, combustion, and emission characteristics of dual-fuel operation using ethanol as a partial substitute for diesel in a direct injection compression ignition engine. The study discovered that adding ethanol to diesel engines reduces peak cylinder pressure and temperature due to its evaporative cooling qualities, with a maximum error of only 2.5%, exhibiting remarkable alignment between simulation and experimental data. The experiment was conducted on a modified single cylinder direct injection CI engine with an ethanol port injector controlled purely by Arduino software. The tests were carried out with different Ethanol substitutions at varied engine loads (0, 20%, 40%, 60%, 80%, and 100%). The study looked at the performance and emissions of a DI CI engine with ethanol substitutes of 10%, 20%, and 30%, with E10 outperforming and E30 outperforming, but caution is urged due to increased energy degradation. E10 and E20 ethanol replacements dramatically cut CO, HC, and NO emissions in diesel engines, improving environmental performance with modest changes.

Early Evaluation of an Ultra-Portable X-ray System for Tuberculosis Active Case Finding.

X-ray screening is an important tool in tuberculosis (TB) prevention and care, but access has historically been restricted by its immobile nature. As recent advancements have improved the portability of modern X-ray systems, this study represents an early evaluation of the safety, image quality and yield of using an ultra-portable X-ray system for active case finding (ACF). We reported operational and radiological performance characteristics and compared image quality between the ultra-portable and two reference systems. Image quality was rated by three human readers and by an artificial intelligence (AI) software. We deployed the ultra-portable X-ray alongside the reference system for community-based ACF and described TB care cascades for each system. The ultra-portable system operated within advertised specifications and radiologic tolerances, except on X-ray capture capacity, which was 58% lower than the reported maximum of 100 exposures per charge. The mean image quality rating from radiologists for the ultra-portable system was significantly lower than the reference (3.71 vs. 3.99, p < 0.001). However, we detected no significant differences in TB abnormality scores using the AI software (p = 0.571), nor in any of the steps along the TB care cascade during our ACF campaign. Despite some shortcomings, ultra-portable X-ray systems have significant potential to improve case detection and equitable access to high-quality TB care.

Enhancing autotrophic nitrogen removal with a novel dissolved oxygen-differentiated airlift internal circulation reactor: Long-term operational performance and microbial characteristics

Autotrophic nitrogen removal (ANR) processes have not been widely applied in wastewater treatment due to their long start-up time and unstable performance. In this study, a novel dissolved oxygen-differentiated airlift internal circulation reactor was developed to enhance ANR from wastewater. During 200 days of continuous operation, the reactor start-up was achieved within 30 days; a high total nitrogen removal efficiency of 80% was achieved and stably maintained under an aeration rate of 0.90 L/min and hydraulic retention time of 6 h. Additionally, the color of sludge went from a light yellow to dark red, and the amount and size of the micro-granules increased obviously. Medium-sized (1.0–2.5 mm) micro-granules accounted for 72.4% on day 190. The specific anammox activity increased from 0.53 to 1.43 g-N/g-VSS/d, while the SNOA decreased from 0.93 to 0.08 g-N/g-VSS/d. Furthermore, the microbial analysis showed that the Nitrosomonas (4.2%) and Candidatus Brocadia (22.6%) were enriched and formed the micro-granules after the reactor's long-term operation. The results indicate that novel configuration realizes the partitioning of dissolved oxygen (DO), optimizes nitritation and anammox reactions, and accelerates biochemical reactions, thereby enhancing ANR performance. This study provides a practical alternative to enhance ANR performance and a scientific basis for the development and application of novel nitrogen removal reactors.

New Performance Modeling Techniques for Photovoltaic Modules and Different Types of Wind Turbines

This paper presents new modeling techniques for evaluating the performance of photovoltaic (PV) panels, vertical-axis wind turbines (VAWT), and horizontal-axis wind turbines (HAWT). Two methods are implemented to evaluate and simulate the designed models based on actual data points from various manufacturing manuals. The first technique is based on curve fitting while the artificial neural network (ANN) is the second method. The developed models can predict the operating performance characteristics of PV, VAWT and HAWT based only on the demand power. Hence, it can easily assist the designer to select a suitable unit before the installation process. The PV model can predict the short circuit current, open circuit voltage, voltage and current at maximum power, module efficiency and the module cost for a power range from 5W to 350W per module. Moreover, the wind turbine models can predict the cut-in wind speed, rated speed, rotor diameter, rotor speed, hub height and the turbine cost for a power range of 0.1kW to 100kW for VAWT and from 0.5kW to 8000kW for HAWT. The results show that the ANN method provides a higher match with the actual data compared to the curve fitting method. The models are conducted via Matalb/Simulink.

Assessing the Influence of Compression Ratio on Engine Characteristics Including Operational Limits of a Biogas-Fueled Spark-Ignition Engine

Abstract Biogas, which is a renewable alternative fuel, has high antiknocking properties with the potential to substitute fossil fuels in internal combustion engines. In this study, performance characteristics of a spark-ignition (SI) engine operated under methane (baseline case) and biogas are compared at the compression ratio (CR) of 8.5:1. Subsequently, the effect of CR on operational limits, performance, combustion, and emission characteristics of the engine fueled with biogas is evaluated. A variable compression ratio, spark-ignition engine was operated at various CRs of 8.5:1, 10:1, 11:1, 13:1, and 15:1 over a wide range of operating loads at 1500 rpm. Results showed that the operating range of the engine at 8.5:1 CR reduced when biogas was utilized in the engine instead of methane. However, the operating range of the engine for biogas extended with an increase in CR—an increase from 9.6 N-m-16.5 N-m to 2.8 N-m-15.1 N-m was observed when CR was increased from 8.5:1 to 15:1. The brake thermal efficiency improved from 13.7% to 16.3%, and the coefficient of variation (COV) of indicated mean effective pressure (IMEP) reduced from 12.7% to 1.52% when CR was increased from 8.5:1 to 15:1 at 8 N-m load. The emission level of carbon dioxide was decreased with an increase in CR due to an improvement in the thermal efficiency and the combustion process.

Performance analysis of a solar-aided coal-fired power plant in off-design working conditions and dynamic process

Solar-aided coal-fired power generation is a promising technique to reduce cost and enhance the efficiency of concentrated solar power. Operation optimization is important but has difficulty improving the performance of solar-aided coal-fired power plants, due to the fluctuations in power load and solar energy. Therefore, the operation performance and dynamic characteristics of a solar-aided coal-fired power plant were investigated in this study. A model of the plant including trough collector system and coal-fired plant was developed. A case was studied to demonstrate the model practicability on basis of a 600 MW supercritical coal-fired plant and a trough collector system integrated in parallel with #2 and #3 high pressure heaters of regenerative system. Under different solar irradiances, operation characteristics were analyzed from 100% to 50% loads with varying ratio of feedwater to trough collector system. The solar-to-electricity efficiency under different off-design conditions was obtained. Moreover, the dynamic response characteristics of solar-aided coal-fired power plant were studied with the disturbances of direct normal irradiance and ratio of feedwater to trough collector system. Results showed that the solar-to-electricity efficiency in design condition was 25.80%. The adjustment of the ratio of feedwater to trough collector system could lead to an optimized operation. Furthermore, the dynamic characteristics of trough collector system and solar-aided coal-fired power plant were analyzed. The results are expected to guide the control optimization of solar-aided coal-fired power plant.

Off-design performance characteristics study on ISCC system with solar direct steam generation system

Integrated solar combined cycle (ISCC) system can make full use of solar energy, improves the system thermal efficiency and reduces the fossil fuel consumption. In this paper, the model of ISCC system is established by using the Aspen Plus and Ebsilon. The off-design operation performance characteristics of the gas turbine cycle (GTC), steam turbine cycle (STC) and ISCC system are investigated under different gas turbine off-design operation modes. And the thermal performances of ISCC system under different environmental conditions are also analyzed. The research results show that the impact of the gas turbine off-design operation mode on the STC is more significant than that on the GTC, so in order to obtain the optimum operation performance of the ISCC under off-design conditions, the inlet guided valve (IGV) of air compressor should be adjusted accordingly, which can ensure that the efficiency of STC keeps at a high level. The effect of environmental conditions on the GTC is greater than that on the STC. The influence of the ambient temperature on ISCC system is greater than the influence of DNI on ISCC system. The achievements from this paper will provide valuable references for system design and operation optimization of ISCC system.

Design and Vibration Optimization of Direct Current Motor of Permanent Magnet of Rectangular Magnetic Steel

Direct current motor of permanent magnet (PMDCM) is widely used at present. To optimize its operating performance and vibration characteristics, a new PMDCM of rectangular magnetic steel was developed. The co-simulation was conducted based on RMxprt and MAXWELL. The simulation results verify that the output power and torque meet the design requirements. Then the cogging torque of the designed motor was analyzed and optimized by using response surface method. The influence degree of each factor on cogging torque was analyzed. When factor A, the factor B, and factor C are 33.51mm, 2.42mm, and 1.50mm, the root-mean-square (RMS) value and the maximum value of the cogging torque are smallest. The fitting accuracy of the two regression equations of RMS and maximum cogging torque is 94.30% and 97.26%. To further verify the correctness of analysis results, the optimized motor and reference motor were manufactured and the vibration velocity data at different positions were measured. The measured data shows that the maximum and average data of vibration velocity at measuring point 1 are decreased by 18.99% and 19.03% and the maximum and average vibration velocity at measuring point 2 are decreased by 9.73% and 4.70%. The method of vibration reduction is effective. The proposed optimization scheme and method may be extended to other motor for reducing vibration.